Version discovery document & catalog/auth-projects endpoint gaps

[gtema]

Evidence: tempest identity compatibility run on PR #998 (skaffold verify -m tempest). Against keystone-rs (all pass against keystone-py):

tempest.api.identity.v3.test_api_discovery.TestApiDiscovery:

• test_api_media_types
• test_api_version_resources
• test_identity_v3_existence
• test_list_api_versions

(These read the root GET / and GET /v3 version-discovery documents; a KeyError: 'media-types' was observed in the debug log, suggesting a field the tempest client expects — media-types in the version resource — isn't present in keystone-rs's discovery document.)

tempest.api.identity.v3.test_catalog.IdentityCatalogTest.test_catalog_standardization — 404 GET observed in the debug log.

tempest.api.identity.v3.test_projects.IdentityV3ProjectsTest.test_list_projects_returns_only_authorized_projects — 404 GET observed, likely /v3/auth/projects (list projects available to the current token) not being implemented/routed.

Needs a focused debug run to confirm each: --regex 'test_api_discovery\.|test_catalog\.|v3\.test_projects\.IdentityV3ProjectsTest' with full debug output.

Tracked via the tempest skaffold module added in #998; re-run skaffold verify -m tempest -a build.artifacts -v debug to reproduce.