Support controller runtime v0.15.0

[thisthat]

Breaking Change ⚠️

Bumping this means we also bump our dependency on K8s - we support 1.26 but drop official support for 1.24

Goal

Bump our dependency on controller-runtime to v0.15.0

Details

The new controller runtime v0.15.0 will introduce multiple breaking changes that will require code refactoring/changes in all our operators:

• the server struct for the webhooks is now an interface, so we need to change all reference of it since we use it to override configs when setting up certificates
• the decoder injector has been removed this means we need to pass one to the webhooks explicitly - tackled in Remove Decoder Injector interface from webhook #1445
• few ways to set up the controller manager are deprecated: setting up the port can be done using WebhookServer.Port, and disabling caching shall use Client.Cache.DisableCacheFor.
• adapt tests according to this breaking change: ⚠️ Fakeclient: Fix status handling kubernetes-sigs/controller-runtime#2259
• Unit tests for the controllers need to be adapted as well

DoD

• KLT depends on v0.15.0 of controller-runtime
• Documentation is updated on which K8s versions are supported

Depends on

• Remove Decoder Injector interface from webhook #1445

Resources

• Breaking changes list: https://github.com/kubernetes-sigs/controller-runtime/releases/tag/v0.15.0

[geoffrey1330]

Hi @thisthat could you please assign this issue to me so i can look into it.

[thisthat]

Sure! Thanks @geoffrey1330

[mowies]

Also documentation should be updated with the new k8s version requirements

The doc to be updated is Supported Kubernetes Versions.

We need to create a table now, similar to that in the Keptn v1 Supported Versions to preserve info about k8s versions supported for 0.8.0 and earlier.

[RealAnna]

@geoffrey1330 there are quite a few complications due to a container-runtime bug in the fake client, we have this on hold so I will unassign you for now and close your pr.