fix(validators): allow GitLab URLs with nested subgroups

[truecallerabreham]

Summary

The gitlabURLRegex in internal/validators/utils.go only allows two path segments (owner/repo), rejecting valid GitLab URLs with subgroups like:

https://gitlab.com/myorg/team/subgroup/my-mcp-server

GitLab subgroups are a standard feature used in GitLab Enterprise. The current regex prevents self-hosted registries from publishing servers whose source lives in a GitLab group hierarchy.

Changes

• Updated gitlabURLRegex to allow any number of path segments: [\w.-]+(/[\w.-]+)*
• Added unit tests for GitLab URLs with 1, 2, and 3 levels of subgroups
• Added comprehensive test suite for IsValidRepositoryURL function

Test Plan

• Added unit tests for subgroup URLs
• Run go test ./internal/validators/... (requires Go installation)

Related

Fixes #1359

[nbeai]

Thanks for adding subgroup coverage. One thing I think may fail in the new table test: the updated GitLab regex now allows a single path segment (gitlab.com/owner), because (/[\w.-]+)* can repeat zero times. That seems to conflict with the new GitLab URL missing repo case expecting false.

Maybe the pattern should still require at least two path segments, then allow extra subgroup segments after that, e.g. .../[\w.-]+/[\w.-]+(/[\w.-]+)*/?$.

[rdimitrov]

Thanks for taking this on! We ended up with two PRs for the same GitLab nested-subgroup fix (this one and #1361). #1361 is passing CI and its regex requires at least owner+repo, whereas the pattern here also matches a single-segment path like gitlab.com/owner (which is what's turning the tests red). To keep things simple I would prefer we work with #1361 and close this one.