Adds quota information to Prometheus metrics

[thoraxe]

Description

• Add QuotaMetricsRepository with PostgreSQL implementation for data access
• Add QuotaMetricsCollector with 6 new Prometheus metrics:
  • ols_quota_limit_total, ols_quota_available_total, ols_quota_utilization_percent
  • ols_token_usage_total, ols_quota_warning_subjects_total, ols_quota_exceeded_subjects_total
• Add QuotaMetricsService with FastAPI dependency injection and singleton pattern
• Add QuotaMetricsScheduler for automatic background updates (5-minute intervals)
• Integrate with existing /metrics endpoint for seamless monitoring
• Add comprehensive test coverage with 42 unit tests across 4 test files
• Update README.md with detailed metrics documentation

Features:

• Real-time quota utilization monitoring for users and clusters
• Token usage tracking by provider/model with privacy considerations
• Automatic threshold detection (warning >80%, exceeded >100%)
• Graceful error handling with circuit breaker patterns
• Health checks and database reconnection logic
• Background scheduler with configurable update intervals

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

Type of change

• Refactor
• New feature
• Bug fix
• CVE fix
• Optimization
• Documentation Update
• Configuration Update
• Bump-up dependent library
• Bump-up library or tool used for development (does not change the final image)
• CI configuration change
• Konflux configuration change

Related Tickets & Documents

• Closes https://issues.redhat.com/browse/OLS-1653

Checklist before requesting a review

• I have performed a self-review of my code.
• PR has passed all pre-merge test jobs.
• If it is a core feature, I have added thorough tests.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign xrajesh for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[raptorsun]

/retest

[openshift-ci]

@thoraxe: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/integration	aba67d7	link	true	/test integration
ci/prow/4.18-e2e-ols-cluster	aba67d7	link	true	/test 4.18-e2e-ols-cluster
ci/prow/e2e-ols-cluster	aba67d7	link	true	/test e2e-ols-cluster

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.