kubernetes: Add provider + namespace resource

[radeksimko]

I intentionally made this PR as minimal as possible (provider + 1 resource + relevant tests + docs) to make it easier for review. Other resources and potentially data sources may follow.

Test plan

make testacc TEST=./builtin/providers/kubernetes
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/02 11:54:13 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/kubernetes -v  -timeout 120m
=== RUN   TestProvider
--- PASS: TestProvider (0.00s)
=== RUN   TestProvider_impl
--- PASS: TestProvider_impl (0.00s)
=== RUN   TestAccKubernetesNamespace_basic
--- PASS: TestAccKubernetesNamespace_basic (6.66s)
=== RUN   TestAccKubernetesNamespace_importBasic
--- PASS: TestAccKubernetesNamespace_importBasic (5.78s)
=== RUN   TestAccKubernetesNamespace_generatedName
--- PASS: TestAccKubernetesNamespace_generatedName (5.63s)
=== RUN   TestAccKubernetesNamespace_importGeneratedName
--- PASS: TestAccKubernetesNamespace_importGeneratedName (6.14s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/kubernetes	24.288s

History Lesson

There have been a couple of PRs with K8S provider in the past:

• Add Kubernetes provider #3132
• [WIP] Add Kubernetes provider #3453
• provider/kubernetes: Pods resource spec is finished #3471
• provider/kubernetes: Pods Resource CRUD operations implemented #3584

which were closed (unmerged) for a number of reasons, TL;DR:

• representing object specs as JSON string turned out to have some significant flaws - Add Kubernetes provider #3132 (comment)
• some resources have significantly complex & nested schemas which in turn makes maintenance of the TF schema & relevant docs difficult - provider/kubernetes: Pods resource spec is finished #3471

Both mentioned things are being addressed in https://github.com/radeksimko/terraform-gen, although we might not be able to address these as well as I'd hope, mainly because the source SDK structs aren't concrete enough for our schema (e.g. validation, list vs set, hashing mechanisms etc.). But at least folks can get going quickly from zero, generate skeleton of schema + docs and then modify and do the rest manually.

[paddycarver]

Spent a couple days reviewing this in depth and reading up on the history, and it gets a 👍 from me. :)

[radeksimko]

Thanks Paddy, I appreciate the extra time invested into the review!

[paddycarver]

My pleasure! Sorry for the delay, I got confused and wanted to understand done background before signing off on it.

[pires]

Shouldn't client-go be used instead?

[radeksimko]

I really wanted to use that library when starting the work on K8S provider, but it was practically impossible to use it as a vendored dependency due to some upstream issues/conflicts which I described in #12230 (comment)

We might switch to that library at some point in the future to reduce the number of vendored LOC and because that's the library that should be used for that purpose, but the main goal is to get initial coverage of all stable (v1) k8s resources for now so re-vendoring is not currently on my radar.

I hope that's understandable 😃

[pires]

Totally understandable. Keep up!

[ghost]

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