Add support for service minscale annotation

[Alexander-Kita]

Fixes #14184

Proposed Changes

• Add servicescaler controller that implements route reconciler to apply service minscale

Release Note

Adds service min scale capability

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Alexander-Kita
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[knative-prow]

Hi @Alexander-Kita. Thanks for your PR.

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[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 34 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.20%. Comparing base (7c94473) to head (3b6cf3d).

Files with missing lines	Patch %	Lines
pkg/reconciler/servicescaler/servicescaler.go	81.37%	10 Missing and 9 partials ⚠️
pkg/apis/autoscaling/v1alpha1/pa_lifecycle.go	0.00%	5 Missing and 1 partial ⚠️
pkg/testing/v1/route.go	0.00%	5 Missing ⚠️
pkg/apis/serving/metadata_validation.go	71.42%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16574      +/-   ##
==========================================
- Coverage   80.36%   80.20%   -0.17%     
==========================================
  Files         217      219       +2     
  Lines       17305    13709    -3596     
==========================================
- Hits        13907    10995    -2912     
+ Misses       3035     2340     -695     
- Partials      363      374      +11     

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[dprotaso]

/ok-to-test

[dprotaso]

I was thinking we just use the existing min-scale annotation (without the service- prefix)

[dprotaso]

Then we wouldn't need to adjust the KPA code etc.

What were your thoughts about having it separate?

[Alexander-Kita]

Originally I tried this. However, if the user removes the service minscale annotation from the service or route and updates, I could not find a good way to determine what the original revision minscale was since it was overwritten.