Added generated OpenAPI client to GARM

[yhaliaw]

What this PR does

This PR targets the GARM charm.

• Add a script to generate the GARM HTTP API client with OpenAPI Generator. The generator image is pinned to a stable release tag (v7.23.0) in sync with .openapi-generator/VERSION.
• The generated code is checked into this repo.
• Added a GARM API client class that uses the generated code. Currently, it supports the /first_run API, which is used to register a user on first run of GARM.
• Modify charm.py to ensure the first run API is called once. GARM is served on a single fixed port (8080); _maybe_first_run connects via loopback using GARM_PORT and correctly wraps IPv6 addresses in [...].
• First-run initialisation is gated to the leader unit to prevent race conditions on multi-unit deployments.
• Merged with main branch changes: _workload_config pins the workload port to GARM_PORT and disables the framework's default metrics scrape job (metrics are declared in paas-config.yaml).

Why we need it

Standardize the API calling process in the GARM charm.
Register the user of GARM in the GARM charm.

Checklist

• Changes comply with the project's coding standards and guidelines (see CONTRIBUTING.md and STYLE.md)
• CONTRIBUTING.md has been updated upon changes to the contribution/development process (e.g. changes to the way tests are run)
• Technical author has been assigned to review the PR in case of documentation changes (usually *.md files)
• I updated docs/changelog.md with user-relevant changes
• I used AI to assist with preparing this PR
• I added or updated tests as needed (unit and integration)
• If integration test modules are used: I updated the workflow configuration
  (e.g., in .github/workflows/integration_tests.yaml, ensure the modules list is correct)
• If this PR involves a Grafana dashboard: I added a screenshot of the dashboard
• If this PR involves Terraform: terraform fmt passes and tflint reports no errors
• If this PR involves Rockcraft: I updated the version

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Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 8 comments.

[Copilot]

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 5 comments.

[yhaliaw]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved in the latest commit. Three files had conflicts:

• charms/garm/src/charm.py: Kept _workload_config from main (replacing _listen_port), updated _maybe_first_run to use GARM_PORT directly, and dropped the listen_address argument from the render_garm_toml call.
• charms/tests/integration/test_garm.py: Kept GARM_ADMIN_CREDENTIALS_LABEL, updated GARM_API_PORT to 8080, preserved the admin-credentials assertions from this branch, and added the new test_garm_metrics_endpoint_no_auth test from main.
• docs/changelog.md: Kept both entries with the 2026-06-15 entry first.

All 25 unit tests pass.

[yanksyoon]

Minor comments, LGTM.