fix(controller): handle error for invalid osp

[oliverbaehler]

What this PR does / why we need it:

I have created my own CustomOperatingSystemProfile and attempted to use it in my clusters. However whenever a MachineDeployment was associated with the profile the osm controller started crashing because of an uncaught nil pointer:

$ kubectl logs -f operating-system-manager-f849789b8-hgk7w -n cluster-n57gh8qjcd
Defaulted container "operating-system-manager" out of: operating-system-manager, copy-http-prober (init)
{"level":"info","time":"2024-06-10T17:43:43.487Z","logger":"http-prober","caller":"http-prober/main.go:137","msg":"Probing","attempt":1,"max-attempts":100,"target":"https://apiserver-external.cluster-n57gh8qjcd.svc.cluster.local./healthz"}
{"level":"info","time":"2024-06-10T17:43:43.491Z","logger":"http-prober","caller":"http-prober/main.go:126","msg":"Hostname resolved","hostname":"apiserver-external.cluster-n57gh8qjcd.svc.cluster.local.","address":"10.100.3.234:443"}
{"level":"info","time":"2024-06-10T17:43:43.494Z","logger":"http-prober","caller":"http-prober/main.go:150","msg":"Endpoint is available"}
{"level":"info","time":"2024-06-10T17:43:43.518Z","caller":"osm-controller/main.go:309","msg":"starting manager"}
{"level":"info","time":"2024-06-10T17:43:43.519Z","logger":"controller-runtime.metrics","caller":"manager/runnable_group.go:223","msg":"Starting metrics server"}
{"level":"info","time":"2024-06-10T17:43:43.519Z","logger":"controller-runtime.metrics","caller":"manager/runnable_group.go:223","msg":"Serving metrics server","bindAddress":"0.0.0.0:8080","secure":false}
{"level":"info","time":"2024-06-10T17:43:43.519Z","caller":"manager/runnable_group.go:223","msg":"starting server","kind":"health probe","addr":"[::]:8085"}
I0610 17:43:43.519278       1 leaderelection.go:250] attempting to acquire leader lease kube-system/operating-system-manager...
I0610 17:45:13.387812       1 leaderelection.go:260] successfully acquired lease kube-system/operating-system-manager
{"level":"info","time":"2024-06-10T17:45:13.388Z","caller":"controller/controller.go:234","msg":"Starting EventSource","controller":"operating-system-config-controller","source":"kind source: *v1alpha1.MachineDeployment"}
{"level":"info","time":"2024-06-10T17:45:13.388Z","caller":"controller/controller.go:234","msg":"Starting EventSource","controller":"OperatingSystemProfileController","source":"kind source: *v1.Deployment"}
{"level":"info","time":"2024-06-10T17:45:13.388Z","caller":"controller/controller.go:234","msg":"Starting Controller","controller":"operating-system-config-controller"}
{"level":"info","time":"2024-06-10T17:45:13.388Z","caller":"controller/controller.go:234","msg":"Starting Controller","controller":"OperatingSystemProfileController"}
{"level":"info","time":"2024-06-10T17:45:13.490Z","caller":"controller/controller.go:234","msg":"Starting workers","controller":"operating-system-config-controller","worker count":10}
{"level":"info","time":"2024-06-10T17:45:13.491Z","caller":"osc/osc_controller.go:138","msg":"Reconciling OSC resource..","request":"kube-system/practical-blackwell"}
{"level":"info","time":"2024-06-10T17:45:13.593Z","caller":"controller/controller.go:234","msg":"Starting workers","controller":"OperatingSystemProfileController","worker count":10}
{"level":"info","time":"2024-06-10T17:45:13.594Z","caller":"osp/osp_controller.go:105","msg":"Reconciling default OSP resource.."}
{"level":"info","time":"2024-06-10T17:45:13.594Z","caller":"osp/osp_controller.go:105","msg":"Reconciling default OSP resource.."}
{"level":"info","time":"2024-06-10T17:45:13.594Z","caller":"osp/osp_controller.go:105","msg":"Reconciling default OSP resource.."}
{"level":"info","time":"2024-06-10T17:45:13.594Z","caller":"osp/osp_controller.go:105","msg":"Reconciling default OSP resource.."}
{"level":"info","time":"2024-06-10T17:45:13.690Z","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-flatcar"}
{"level":"info","time":"2024-06-10T17:45:13.707Z","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-amzn2"}
{"level":"info","time":"2024-06-10T17:45:13.797Z","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-rockylinux"}
{"level":"info","time":"2024-06-10T17:45:13.899Z","caller":"runtime/panic.go:770","msg":"Observed a panic in reconciler: runtime error: invalid memory address or nil pointer dereference","controller":"operating-system-config-controller","object":{"name":"practical-blackwell","namespace":"kube-system"},"namespace":"kube-system","name":"practical-blackwell","reconcileID":"2b09108a-c84b-4114-b88e-5aad7b00b559"}
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x130 pc=0x15f6c40]

goroutine 305 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:116 +0x1e5
panic({0x177e000?, 0x28da590?})
	runtime/panic.go:770 +0x132
k8c.io/operating-system-manager/pkg/controllers/osc.(*Reconciler).reconcileOperatingSystemConfigs(0xc00034e680, {0x1c665b8, 0xc000711bf0}, 0xc00035f408)
	k8c.io/operating-system-manager/pkg/controllers/osc/osc_controller.go:272 +0x8e0
k8c.io/operating-system-manager/pkg/controllers/osc.(*Reconciler).reconcile(0xc00034e680, {0x1c665b8, 0xc000711bf0}, 0xc00035f408)
	k8c.io/operating-system-manager/pkg/controllers/osc/osc_controller.go:184 +0xdd
k8c.io/operating-system-manager/pkg/controllers/osc.(*Reconciler).Reconcile(0xc00034e680, {0x1c665b8, 0xc000711bf0}, {{{0xc000a02180, 0xb}, {0xc00079e5a0, 0x13}}})
	k8c.io/operating-system-manager/pkg/controllers/osc/osc_controller.go:166 +0x405
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0x1c6a578?, {0x1c665b8?, 0xc000711bf0?}, {{{0xc000a02180?, 0xb?}, {0xc00079e5a0?, 0x0?}}})
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:119 +0xb7
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc00072b680, {0x1c665f0, 0xc0005df630}, {0x17fe720, 0xc000020860})
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:316 +0x3bc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc00072b680, {0x1c665f0, 0xc0005df630})
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:266 +0x1be
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:227 +0x79
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2 in goroutine 278
	sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:223 +0x50c

And

operating-system-manager-f849789b8-hgk7w             0/1     CrashLoopBackOff   233 (3m3s ago)   20h

Making it impossible to lifecycle other nodes in that cluster. This change catches the error and returns an error. If we implement that, it would also be quickly clear, that I am just too dumb to write profiles:

...
vel":"info","time":"2024-06-10T19:45:31.402+0200","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-rockylinux"}
{"level":"info","time":"2024-06-10T19:45:31.403+0200","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-rhel"}
{"level":"info","time":"2024-06-10T19:45:31.492+0200","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-ubuntu"}
{"level":"info","time":"2024-06-10T19:45:31.492+0200","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-amzn2"}
{"level":"info","time":"2024-06-10T19:45:31.593+0200","caller":"reconciling/ensure.go:165","msg":"updated resource","kind":"v1alpha1.OperatingSystemProfile","namespace":"kube-system","name":"osp-flatcar"}
{"level":"error","time":"2024-06-10T19:45:31.648+0200","caller":"osc/osc_controller.go:167","msg":"Reconciling failed","error":"failed to reconcile operating system config: failed to generate OSC: failed to render bootstrapping file templates: failed to populate OSP file template: failed to parse OSP file [/opt/bin/node-start.sh] template: template: /opt/bin/node-start.sh:3: unexpected \"\\\\\" in template clause"}
{"level":"error","time":"2024-06-10T19:45:31.648+0200","caller":"controller/controller.go:261","msg":"Reconciler error","controller":"operating-system-config-controller","controllerGroup":"cluster.k8s.io","controllerKind":"MachineDeployment","MachineDeployment":{"name":"practical-blackwell","namespace":"kube-system"},"namespace":"kube-system","name":"practical-blackwell","reconcileID":"b6c9d8c9-e19f-4949-b94b-a308ea27cbf8","error":"failed to reconcile operating system config: failed to generate OSC: failed to render bootstrapping file templates: failed to populate OSP file template: failed to parse OSP file [/opt/bin/node-start.sh] template: template: /opt/bin/node-start.sh:3: unexpected \"\\\\\" in template clause"}

However since there is no previous validation for the profile or anything like that and it's directly replicated to all seed clusters which may cause partial degradation of kubermatic components (OSM) we should probably just handle that error.

Which issue(s) this PR fixes:

Fixes #

What type of PR is this?

Special notes for your reviewer:

Does this PR introduce a user-facing change? Then add your Release Note here:

NONE

Documentation:

NONE

[kubermatic-bot]

Hi @oliverbaehler. Thanks for your PR.

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[ahmedwaleedmalik]

/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 07334420f5313de51ec7b2d78a195fb8a93d8442

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[ahmedwaleedmalik]

/cherry-pick release/v1.5

[kubermatic-bot]

@ahmedwaleedmalik: new pull request created: #397

In response to this:

/cherry-pick release/v1.5

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