feat: func domain route

[lkingland]

• 🎁 func --domain to choose routes

Adds the --domain flag which, when provided sets the value of the func.domain label on the deployed knative service. The cluster can then use this to choose which route to create for multi-route clusters. Optional.

Note that this will have no effect unless the cluster is configured to apply routes based on a domain mapping in the config-domain config map. This feature is functional in dev and a future PR will add this configuration both to the cluster created via CI/CD.

Documenting this feature is still an open question, but here us an example of a cluster configuration which by default exposes functions internally only as function.namespace.cluster.local, and allows for functions to be selectively exposed using the --domain flag for boson-project.org or boson-project.net:

  cluster.local: ""
  boson-project.org: |
    selector:
      func.domain: "boson-project.org"
  boson-project.net |
    selector:
      func.domain: "boson-project.net"

/kind enhancement

[knative-prow]

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[codecov]

Codecov Report

Patch coverage: 91.17% and project coverage change: +1.69 🎉

Comparison is base (1ba7015) 61.26% compared to head (8c74121) 62.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1690      +/-   ##
==========================================
+ Coverage   61.26%   62.95%   +1.69%     
==========================================
  Files          93       93              
  Lines       12049    12189     +140     
==========================================
+ Hits         7382     7674     +292     
+ Misses       4004     3818     -186     
- Partials      663      697      +34     

Flag	Coverage Δ
e2e-test	39.04% <91.17%> (-0.17%)	⬇️
e2e-test-oncluster	34.41% <91.17%> (?)
e2e-test-oncluster-runtime	29.56% <91.17%> (?)
e2e-test-runtime-go	28.15% <91.17%> (?)
e2e-test-runtime-node	29.26% <91.17%> (?)
e2e-test-runtime-python	29.26% <91.17%> (?)
e2e-test-runtime-quarkus	29.40% <91.17%> (?)
e2e-test-runtime-springboot	28.30% <91.17%> (?)
e2e-test-runtime-typescript	29.40% <91.17%> (?)
integration-tests	49.98% <91.17%> (-0.24%)	⬇️
unit-tests-macos-latest	48.72% <91.17%> (-0.35%)	⬇️
unit-tests-ubuntu-latest	49.62% <91.17%> (-0.36%)	⬇️
unit-tests-windows-latest	48.77% <91.17%> (-0.35%)	⬇️

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

Impacted Files	Coverage Δ
pkg/functions/function.go	79.34% <ø> (+1.42%)	⬆️
pkg/knative/deployer.go	64.20% <0.00%> (-4.35%)	⬇️
cmd/deploy.go	76.09% <100.00%> (+0.98%)	⬆️

... and 14 files with indirect coverage changes

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[lkingland]

Note, related to #1666, it would be best if we had a way to inspect the state of the current platform upon which the function will be deployed, and issue a warning if this flag will not work as intended, and ideally have a tab-completion UX for choosing the domain for the function's route when more than one are configured.

[lance]

/lgtm

This is a nice addition which will also be useful in clusters that have staging and/or test domains.