Add more tests to the resource controller

[frewilhelm]

Description

In https://github.com/open-component-model/ocm-k8s-toolkit/pull/30 only one test is created. However, we need more tests to have an appropriate code coverage.

• Refactor BeforeFunc-parts to be more generic
• Add tests that
  • reconciliation works as planned
  • reconciliation stops when requirements are not met
  • reconciliation starts again when the resource changes
  • reconciliation starts again when component changes
  • reconciliation starts again when artifact (owned by resource-controller) changes
  • check downgradibility (if this is applicable in this context?)
  • finalizers is added/removed/used
• Unit tests for helper functions in resource controller

Done Criteria

• ...
• Code has been reviewed by other team members
• Internal technical Documentation created/updated
• New / changed code is documented
• Analysis of existing tests (Unit and Integration)
• Unit Tests created for new code or existing Unit Tests updated
• Integration Test Suite updated (includes deletion of existing unnecessary Integration Test and/or creation of new ones if required)
• Enduser Documentation updated (if applicable)
• Successful demonstration in Review