[CECO-1763] Controller for generic custom resource

[tbavelier]

What does this PR do?

Introduces a generic controller relying on Datadog Go client to handle CRUD operations on multiple resources. Initial support includes notebooks and synthetics (api/browser tests).
Examples:

apiVersion: datadoghq.com/v1alpha1
kind: DatadogGenericResource
metadata:
  name: api-test
spec:
    type: synthetics_api_test
    jsonSpec: |-
        {
           [...]
        }

apiVersion: datadoghq.com/v1alpha1
kind: DatadogGenericResource
metadata:
  name: notebook
spec:
    type: notebook
    jsonSpec: |-
        {
           [...]
        }

Additional Notes

Next steps:

• Document fully-fledged examples
• Document onboarding strategy (e.g. export current resource from the API, create the associated YAML, deploy them)
• Document internally how to add new resources
• UI button to export to manifest
• Add option to start the controller in the Helm chart

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

Describe your test plan

1. Include datadogGenericResourceEnabled=true in args for the manager container to enable the controller, as well as DD_API_KEY and DD_APP_KEY in the envs
2. Deploy examples
3. Update their jsonSpec
4. Ensure the changes are reflected in the UI
5. Delete the resources
6. Ensure they are removed from the UI

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 39.47368% with 299 lines in your changes missing coverage. Please review.

Project coverage is 48.75%. Comparing base (db00883) to head (df68861).

Files with missing lines	Patch %	Lines
...al/controller/datadoggenericresource/controller.go	38.97%	74 Missing and 9 partials ⚠️
...nternal/controller/datadoggenericresource/utils.go	57.05%	67 Missing ⚠️
...al/controller/datadoggenericresource/synthetics.go	0.00%	48 Missing ⚠️
...nal/controller/datadoggenericresource/notebooks.go	17.02%	39 Missing ⚠️
...al/controller/datadoggenericresource_controller.go	0.00%	15 Missing ⚠️
pkg/datadogclient/client.go	0.00%	14 Missing ⚠️
cmd/main.go	0.00%	12 Missing ⚠️
internal/controller/setup.go	31.25%	11 Missing ⚠️
...nal/controller/datadoggenericresource/finalizer.go	74.35%	7 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1534      +/-   ##
==========================================
- Coverage   48.94%   48.75%   -0.20%     
==========================================
  Files         227      235       +8     
  Lines       20636    21120     +484     
==========================================
+ Hits        10101    10296     +195     
- Misses      10010    10287     +277     
- Partials      525      537      +12     

Flag	Coverage Δ
unittests	48.75% <39.47%> (-0.20%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...datadoghq/v1alpha1/datadoggenericresource_types.go	100.00% <100.00%> (ø)
...oghq/v1alpha1/datadoggenericresource_validation.go	100.00% <100.00%> (ø)
...nal/controller/datadoggenericresource/finalizer.go	74.35% <74.35%> (ø)
internal/controller/setup.go	49.33% <31.25%> (-2.16%)	⬇️
cmd/main.go	0.00% <0.00%> (ø)
pkg/datadogclient/client.go	0.00% <0.00%> (ø)
...al/controller/datadoggenericresource_controller.go	0.00% <0.00%> (ø)
...nal/controller/datadoggenericresource/notebooks.go	17.02% <17.02%> (ø)
...al/controller/datadoggenericresource/synthetics.go	0.00% <0.00%> (ø)
...nternal/controller/datadoggenericresource/utils.go	57.05% <57.05%> (ø)
... and 1 more

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[levan-m]

Any way to avoid this in the prod code?

[tbavelier]

We could mock an HTTP client for the CRUD Go api, so we send requests there instead of the real API/a non existing client but that would be more convoluted/a general improvement for other controllers to have this mock server/client for API requests

[levan-m]

Left some suggestions/nits. Overall looks good but handling of multiple resource APIs (in utils.go) can be refactored to more maintainable code.