WPB-22168 backend new feature flag cells internal

[battermann]

https://wearezeta.atlassian.net/browse/WPB-22168

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[Copilot]

Pull request overview

This PR introduces a new feature flag cellsInternal that complements the existing cells feature flag. The split is intentional: cells is controlled by team admins, while cellsInternal is managed exclusively by site operators/customer support via the internal API. This internal configuration holds backend URLs, Collabora edition settings, and storage quotas for the Cells integration.

Key changes:

• Added CellsInternalConfig feature flag with custom validation requiring enabled/unlocked status
• Implemented GET endpoint for public API and full GET/PUT/PATCH endpoints for internal API
• Added comprehensive test coverage including event testing and validation checks

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
libs/wire-api/src/Wire/API/Team/Feature.hs	Defines CellsInternalConfig with nested types (CollaboraEdition, CellsCollabora, CellsBackend, NumBytes, CellsStorage) and schema validation for quota bytes
libs/wire-api/src/Wire/API/Routes/Public/Galley/Feature.hs	Adds public GET endpoint for CellsInternalConfig
libs/wire-api/src/Wire/API/Error/Galley.hs	Adds InvalidStatusUpdate error for validation failures
services/galley/src/Galley/API/Teams/Features.hs	Implements SetFeatureConfig instance with validation enforcing enabled/unlocked status
services/galley/src/Galley/API/Teams/Features/Get.hs	Adds GetFeatureConfig instance for retrieving the configuration
services/galley/src/Galley/API/Public/Feature.hs	Registers the public GET endpoint in the feature API
services/galley/src/Galley/API/Internal.hs	Adds internal API handler for full CRUD operations
libs/galley-types/src/Galley/Types/Teams.hs	Defines FeatureDefaults for CellsInternalConfig
services/galley/galley.integration.yaml	Adds default configuration for integration testing
hack/helm_vars/wire-server/values.yaml.gotmpl	Adds default configuration for Helm deployments
charts/galley/values.yaml	Adds default configuration values for the Helm chart
charts/galley/templates/configmap.yaml	Adds template configuration for the ConfigMap
integration/test/Test/FeatureFlags/CellsInternal.hs	New test module with event, validation, and patch tests
integration/test/Test/FeatureFlags/Cells.hs	Refactored to remove testCellsInternal (moved to dedicated module)
integration/test/Test/FeatureFlags/Util.hs	Updates default feature set to include cellsInternal
integration/integration.cabal	Registers new test module
docs/src/developer/reference/config-options.md	Documents the new feature flag configuration
changelog.d/2-features/WPB-22168	Adds changelog entry for the new feature

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.