feat(lifecycle-operator): introduce RestApiEnabled parameter in KeptnConfig

[asamonik]

Description

Adds a feature flag for the Rest Api

Fixes #3594

Checklist

• My PR fulfills the Definition of Done of the corresponding issue and not more (or parts if the issue is separated
  into multiple PRs)
• I used descriptive commit messages to help reviewers understand my thought process
• I signed off all my commits according to the Developer Certificate of Origin (DCO)
  see Contribution Guide
• My PR title is formatted according to the semantic PR conventions described in
  the Contribution Guide
• My code follows the style guidelines of this project (golangci-lint passes, YAMLLint passes)
• I regenerated the auto-generated docs for Helm and the CRD documentation (if applicable)
• I have performed a self-review of my code
• I have made corresponding changes to the documentation (if needed)
• My changes result in all-green PR checks (first-time contributors need to ask a maintainer to approve their test runs)
• New and existing unit and integration tests pass locally with my changes

[codecov]

Codecov Report

Attention: Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 85.44%. Comparing base (490b2be) to head (7ca0e00).
Report is 127 commits behind head on main.

Files with missing lines	Patch %	Lines
...cycle-operator/controllers/common/config/config.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3620      +/-   ##
==========================================
- Coverage   85.54%   85.44%   -0.10%     
==========================================
  Files         167      167              
  Lines        7414     7419       +5     
==========================================
- Hits         6342     6339       -3     
- Misses        787      794       +7     
- Partials      285      286       +1     

Files with missing lines	Coverage Δ
...ator/controllers/options/keptnconfig_controller.go	85.00% <100.00%> (+0.38%)	⬆️
...cycle-operator/controllers/common/config/config.go	88.23% <0.00%> (-11.77%)	⬇️

... and 1 file with indirect coverage changes

Flag	Coverage Δ
certificate-operator	69.23% <ø> (ø)
component-tests	58.04% <ø> (-0.33%)	⬇️
lifecycle-operator	84.62% <20.00%> (-0.08%)	⬇️
metrics-operator	88.32% <ø> (ø)
scheduler	34.90% <ø> (ø)

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

[mowies]

@asamonik please regenerate the CRD docs, like described here

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud