WPB-23789: Introduce type class for Galley/Action

[blackheaven]

https://wearezeta.atlassian.net/browse/WPB-23789

Checklist

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

[battermann]

LGTM, only one suggestion to make the changelog cleaner.

[Copilot]

Pull request overview

Refactors Galley conversation action handling by replacing the large type-family-based constraint mapping with a local type class (IsConversationAction), moving per-action effect constraints and Galley error rows into instances to support incremental migration away from singletons and towards wire-subsystems.

Changes:

• Introduce IsConversationAction with associated types for action-specific effects and Galley error rows, and implement instances per action tag.
• Refactor updateLocalConversation* wrappers to delegate to updateLocalConversation without passing an explicit performAction callback.
• Update removeMemberFromChannel constraints and consolidate internal changelog entries into a single file.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
services/galley/src/Galley/API/Action.hs	Introduces IsConversationAction and refactors action execution to dispatch via type class instances.
services/galley/src/Galley/API/Update.hs	Adjusts effect constraints for channel member removal path to include NoChanges.
changelog.d/5-internal/WPB-23789-wrap-update-sing	Removes superseded internal changelog entry (now consolidated).
changelog.d/5-internal/WPB-23789-inline-perform-action	Removes superseded internal changelog entry (now consolidated).
changelog.d/5-internal/WPB-23789	Adds consolidated internal changelog entry describing the refactor.

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