Add domain validation to catch invalid names before build/deploy

[RayyanSeliya]

Changes

• 🎁 Add early domain validation with user-friendly error messages
• 🐛 Prevent wasted build time when using invalid domain names
• 🧹 Add comprehensive unit tests for domain validation

Adds DNS-1123 subdomain validation for domain names before build/deploy operations. Invalid domain names now fail immediately with clear error messages instead of proceeding through lengthy builds.

Implementation:

• Add ValidateDomain() function using Kubernetes DNS-1123 subdomain validation (pkg/utils/names.go)
• Add validation check in deployConfig.Validate() and error handling in runDeploy() (cmd/deploy.go)
• Add ErrInvalidDomain error type (pkg/functions/errors.go) with user-friendly CLI message
• Add comprehensive test coverage with 49+ test cases covering valid/invalid domains

Fixes #3151

Before:

$ func deploy --registry ghcr.io/user --domain "my app.com"
Building function image
Still building
^CError: executing lifecycle: context canceled

After:

$ func deploy --registry ghcr.io/user --domain "my app.com"
Error: invalid domain

Domain names must be valid DNS subdomains:
  - Lowercase letters, numbers, hyphens (-), and dots (.) only
  - Start and end with a letter or number
  - Max 253 characters total, each part between dots max 63 characters

Valid examples:
  func deploy --registry ghcr.io/user --domain example.com
  func deploy --registry ghcr.io/user --domain api.example.com

Note: Domain must be configured on your Knative cluster, or it will be ignored.

For more options, run 'func deploy --help'

/kind enhancement

Release Note

Invalid domain names are now caught immediately with helpful error messages, preventing wasted build time

[knative-prow]

Hi @RayyanSeliya. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.22%. Comparing base (0a41919) to head (67f7f32).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3152      +/-   ##
==========================================
+ Coverage   59.41%   60.22%   +0.81%     
==========================================
  Files         134      134              
  Lines       13495    13526      +31     
==========================================
+ Hits         8018     8146     +128     
+ Misses       4537     4408     -129     
- Partials      940      972      +32     

Flag	Coverage Δ
e2e-tests	41.64% <0.00%> (+1.40%)	⬆️
integration-tests	54.67% <53.84%> (+1.68%)	⬆️
unit-tests	46.82% <100.00%> (+0.07%)	⬆️

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[gauron99]

/ok-to-test

[gauron99]

/retest

[RayyanSeliya]

Hey @gauron99 I thinks it's ready now all clear !

[gauron99]

I think it would be better to keep the utils as small as possible, since this PR addresses domains, we need domains only in deploy so it would be better to keep the error definitions in errors and any CLI errors in cmd/deploy.go. And any validation function also to be kept the cmd/deploy.go (where its used)
WDYT @matejvasek @lkingland ?

[lkingland]

/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lkingland, RayyanSeliya

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