Polishing the KeptnConfig implementation

[thisthat]

Goal

Clean up the implementation of KeptnConfig

Technical Details

In the manifests, we are configuring a default URL for the collector but it is ignored since we prefer the value coming from a KeptnConfig. We should make use of the env var to initialize a defaultKeptnConfig until a CRD is reconciled.
Given that we reconcile it, a validation webhook with the following behavior:

• if there is already an existing KeptnConfig CRD
  • if they have the same name, succeed
  • otherwise fail
• otherwise succeed

The RBAC should also be cleaned up:

• RBAC should grant read-only permissions on both, spec and status
• no finalizer is needed

Acceptance Criteria

• Use env vars as defaults
• Introduce a validating webhook
• RBAC is cleaned up

DoD

• Tests for the validating webhook
• Documentation update

[odubajDT]

@thisthat is this ticket done, or is something missing ?

[thisthat]

Hey @odubajDT, the documentation is not yet done. Maybe we can close it with #1239

[odubajDT]

The team agreed that the validating webhook was not needed.