add tag label to HTTPRoute for traffic tag identification

[kahirokunn]

Changes

When a Knative Service has traffic tags, tagged HTTPRoutes are generated but have no metadata indicating which tag they belong to. This makes it difficult for external tools to identify the traffic tag from HTTPRoute resources.

• 🎁 Add networking.internal.knative.dev/tag label to tagged HTTPRoutes

/kind enhancement

Release Note

Add `networking.internal.knative.dev/tag` label to HTTPRoutes so that traffic tags are identifiable from HTTPRoute metadata.

Docs

N/A

Manual testing

Deployed a Knative Service with a traffic tag and confirmed the networking.internal.knative.dev/tag label is present on the tagged HTTPRoute:

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kahirokunn
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[codecov]

Codecov Report

❌ Patch coverage is 70.58824% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.15%. Comparing base (ffc6c4c) to head (3e95149).

Files with missing lines	Patch %	Lines
pkg/reconciler/ingress/resources/helpers.go	64.28%	5 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #931      +/-   ##
==========================================
- Coverage   76.38%   76.15%   -0.23%     
==========================================
  Files          17       17              
  Lines        1266     1296      +30     
==========================================
+ Hits          967      987      +20     
- Misses        263      268       +5     
- Partials       36       41       +5     

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[dprotaso]

This is fragile since the route tag to domain name can be customized.

https://github.com/knative/networking/blob/965e7c322093e04153a4104ebcbaa1f57e4f3505/pkg/config/config.go#L60

see: https://github.com/knative/networking/blob/965e7c322093e04153a4104ebcbaa1f57e4f3505/pkg/config/config.go#L315