WPB-5989 polysemy create client subsystem (part 2)

[battermann]

https://wearezeta.atlassian.net/browse/WPB-5989

In this PR, 4 more operations have been moved to the ClientSubsystem, and unit tests have been added.

The other operations will be move in subsequent PRs.

Checklist

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

[Copilot]

Pull request overview

This PR continues the WPB-5989 migration by moving more client-management behavior behind the Polysemy ClientSubsystem, updating Brig API handlers to call the subsystem, and centralizing a Client -> PubClient conversion helper in wire-api.

Changes:

• Route more Brig public/internal client endpoints through Wire.ClientSubsystem (update/remove/legal hold request + DPoP access token naming).
• Add new ClientSubsystem actions and implement them in the interpreter; expand unit tests accordingly.
• Introduce Wire.API.User.Client.toPubClient and remove duplicate local helpers; drop an unused Brig.Data.Client module.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
services/brig/test/integration/Federation/End2end.hs	Switch expected client list conversion to shared toPubClient.
services/brig/src/Brig/Data/Client.hs	Remove unused/empty module.
services/brig/src/Brig/API/Public.hs	Route update/delete client + public lookups via ClientSubsystem; rename access-token handler.
services/brig/src/Brig/API/Internal.hs	Route legal-hold internal handlers via ClientSubsystem.
services/brig/src/Brig/API/Client.hs	Remove migrated client management exports; keep DPoP access-token logic + prekey endpoints.
services/brig/brig.cabal	Drop Brig.Data.Client from build.
libs/wire-subsystems/test/unit/Wire/Util.hs	Add generators/fixtures for prekeys used by new ClientSubsystem tests.
libs/wire-subsystems/test/unit/Wire/MockInterpreters/ClientStore.hs	Remove local toPubClient helper (but see review comments).
libs/wire-subsystems/test/unit/Wire/ClientSubsystem/InterpreterSpec.hs	Add/expand property tests for add/remove/update + legal-hold flows.
libs/wire-subsystems/src/Wire/ClientSubsystem/Interpreter.hs	Implement RemoveClient, RemoveLegalHoldClient, PublishLegalHoldClientRequested, UpdateClient.
libs/wire-subsystems/src/Wire/ClientSubsystem.hs	Add new effect constructors for client removal/legal-hold/update.
libs/wire-subsystems/src/Wire/ClientStore/Cassandra.hs	Inline PubClient construction and remove redundant helper.
libs/wire-api/src/Wire/API/UserEvent.hs	Derive Show for EventType.
libs/wire-api/src/Wire/API/User/Client.hs	Add shared toPubClient helper.
changelog.d/5-internal/WPB-5989	Update changelog entry with additional PR reference.

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[blackheaven]

I'm not sure how it interacts with Galley's Client code, have you had a look for duplication?

[battermann]

I'm not sure how it interacts with Galley's Client code, have you had a look for duplication?

This is just a refactoring and the intention is not to merge brig's and galley's Client types and code. We can't have galley use the ClientSubsystem easily. Not yet. But I hope soon.