4689:Setup for Threshold TF provider

[matt-metivier]

This PR introduces a new Terraform resource for managing Asserts thresholds configuration via the ThresholdsV2 API.

Changes

New Resource: grafana_asserts_thresholds

• Manages request, resource, and health thresholds through bulk API endpoints
• Supports three threshold types:
  • Request thresholds (error ratios, request rates)
  • Resource thresholds (saturation, resource utilization)
  • Health thresholds (service availability expressions)
• Implements full CRUD operations with proper state management
• Uses singleton pattern with fixed ID for global configuration management

API Client Updates

• Updated grafana-asserts-public-clients from v0.0.0-20250811125322-247815da58ca to v0.0.0-20250911193242-e36893764a50
• Migrated DisabledAlertConfigControllerAPI references to AlertConfigurationAPI due to API consolidation
• Added support for ThresholdsV2 DTOs and endpoints

Technical Details

The resource implements a singleton pattern using a fixed ID (custom_thresholds) since thresholds represent global configuration rather than individual resources. The implementation includes proper error handling, retry logic, and state synchronization with the Asserts API.

Testing

• Unit tests pass for all CRUD operations
• Acceptance tests validate resource lifecycle and state management
• Schema generation and documentation build successfully
• Import functionality verified

Breaking Changes

None. This is a new resource addition with no impact on existing functionality.

[github-actions]

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