fix(garm-configurator): log full config validation error, shorten blocked status

[cbartz]

What this PR does

When config validation fails, garm-configurator put the entire pydantic ValidationError (often multi-line) straight into the unit status message. Juju truncates status messages to their first line, so operators only ever saw the generic header (e.g. 1 validation error for RunnerConfig) with no field/reason, and nothing reached juju debug-log.

This aligns the charm with its siblings (planner-operator, webhook-gateway-operator): the full detail is logged at warning level, and the status is a short, stable Invalid charm config. warning (not error) is used because _reconcile runs on every event, so a persistently misconfigured charm would otherwise spam error-level logs.

Why we need it

The truncated status was actively misleading — an operator hitting an invalid runner option had no way to see which option or why without dumping juju status --format=yaml. The actionable detail now lives in debug-log where operators expect it.

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
• 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
• If this PR adds/removes a charm, or changes a charm's base class, conventions, tooling, or repo structure: I updated the relevant AGENTS.md
• If this PR changes .copilot-collections.yaml or .github/instructions/: I re-checked the AGENTS.md "12-factor divergences" guidance

Test plan

• tox -c tox.toml -e fmt lint static unit all pass in charms/garm-configurator (unit: 51/51).
• Existing invalid-config unit tests (Scenario-based) were updated: they now assert the short Invalid charm config status and that the specific validation detail is emitted as a WARNING log record (via caplog). No parallel tests were added — existing ones were extended.

Review focus

• The status message for all CharmConfigInvalidError paths (not just RunnerConfig) collapses to the single generic Invalid charm config. This is intentional, but reviewers may want to confirm that losing the per-cause status text (e.g. Missing required configuration: openstack-auth-url) is acceptable — that detail now lives only in the log. If a shorter cause-specific status is preferred, that's a larger change to how CharmConfigInvalidError.msg is structured.

Potential breaking changes / new dependencies

None. No new dependencies, APIs, or config options. Behavioral change is limited to status text + log output.

[Copilot]

Pull request overview

This PR improves the operator experience for the garm-configurator charm when charm config validation fails: instead of putting a multi-line Pydantic validation error into Juju status (which gets truncated), it logs the full detail at WARNING level and sets a short, stable Blocked status message.

Changes:

• Log full CharmConfigInvalidError details at WARNING level during _reconcile.
• Collapse Blocked unit status to a stable Invalid charm config message.
• Update Scenario-based unit tests to assert both the short Blocked status and presence of validation detail in warning logs; add a changelog entry.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
docs/changelog.md	Adds a 2026-07-08 entry describing the user-visible status/logging behavior change.
charms/garm-configurator/src/charm.py	Logs config validation details at WARNING and sets a short BlockedStatus message.
charms/garm-configurator/tests/unit/test_charm.py	Updates invalid-config tests to check for the stable status and warning log detail via caplog.

[yanksyoon]

Maybe we can think about how to raise errors that puts charm in blocked status with actionable message. LGTM!

[cbartz]

Maybe we can think about how to raise errors that puts charm in blocked status with actionable message. LGTM!

Thanks. I changed it back to put the full msg in the status.