Add v1beta1 version of DomainMapping crd

[julz]

Adds a v1beta1 version of the DomainMapping CRD and a corresponding group in api + conformance test subdirectory. Also adds the new group to the webhook. I think I'm holding this right, but please review carefully 😅.

[codecov]

Codecov Report

Merging #11682 (fb35e17) into main (0e98289) will increase coverage by 0.05%.
The diff coverage is 90.58%.

@@            Coverage Diff             @@
##             main   #11682      +/-   ##
==========================================
+ Coverage   87.81%   87.87%   +0.05%     
==========================================
  Files         190      196       +6     
  Lines        9275     9360      +85     
==========================================
+ Hits         8145     8225      +80     
- Misses        878      883       +5     
  Partials      252      252              

Impacted Files	Coverage Δ
...kg/apis/serving/v1beta1/domainmapping_lifecycle.go	81.81% <81.81%> (ø)
pkg/apis/serving/v1beta1/conversion_error.go	100.00% <100.00%> (ø)
pkg/apis/serving/v1beta1/domainmapping_defaults.go	100.00% <100.00%> (ø)
pkg/apis/serving/v1beta1/domainmapping_types.go	100.00% <100.00%> (ø)
...g/apis/serving/v1beta1/domainmapping_validation.go	100.00% <100.00%> (ø)
pkg/apis/serving/v1beta1/register.go	100.00% <100.00%> (ø)
pkg/reconciler/configuration/configuration.go	86.15% <0.00%> (-0.77%)	⬇️
... and 5 more

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[julz]

paging @dprotaso to the bat phone: looks like downgrade test is complaining about not being able to downgrade with this change because v1beta1 wouldn't be in the list of versions after downgrade but.. I think that's expected/inevitable when we introduce a new version? Probably missing something obvious, but do you happen to have a good trick for getting past this?

/assign @dprotaso

[dprotaso]

Jul 15 11:10:08.393 install_latest_release [OUT] kapp: Error: Applying update customresourcedefinition/domainmappings.serving.knative.dev (apiextensions.k8s.io/v1) cluster:
1884
Jul 15 11:10:08.393 install_latest_release [OUT]   Updating resource customresourcedefinition/domainmappings.serving.knative.dev (apiextensions.k8s.io/v1) cluster:
1885
Jul 15 11:10:08.393 install_latest_release [OUT]     CustomResourceDefinition.apiextensions.k8s.io "domainmappings.serving.knative.dev" is invalid: status.storedVersions[1]:
1886
Jul 15 11:10:08.393 install_latest_release [OUT]       Invalid value: "v1beta1": must appear in spec.versions (reason: Invalid)

Leave v1alpha1 as the storage version for a release I believe

[julz]

Leave v1alpha1 as the storage version for a release I believe

aha thanks! let's give that a try

[julz]

neat, looked like that worked - thanks @dprotaso

[dprotaso]

nit: copyright date should be 2021

[dprotaso]

/lgtm
/approve

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso, julz

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[dprotaso]

looks like generated clients still have the old copyright date

[julz]

looks like generated clients still have the old copyright date

heh oops, forgot to rebase on my own change :). done

[julz]

existing unrelated flake (#11653)

/retest

[dprotaso]

/lgtm