Release: 2.1.0

[martinmitrevski]

🚀 2.1.0

Make sure to use squash & merge when merging!
Once this is merged, another job will kick off automatically and publish the package.

Bumps Version 27 to 28 and VersionName 2.0.0 to 2.1.0 across the three .uplugin files (StreamChat.uplugin, .5.7, .5.8).

What's in it

• Threads and replies (Threads and replies #157). The write path, GetReplies / QueryThreads / GetThread, per-thread reply storage, FChatThread and the thread list surface, plus long press on a message in the sample to open the reaction picker and the message actions. A minor bump rather than a patch, since this adds API.
• Earlier on main since 2.0.0: the iOS attachment picker moved into a platform folder (Move the iOS picker into a platform folder #156), attachment rendering and composer attachments (Render attachments and attach them from the composer #154), file and image attachments (Add file and image attachments #153).

Docs for the feature: docs-content#1495.

Verification of the released tree

Both engines, strict non-unity builds (-NoPCH -NoSharedPCH -DisableUnity), full automation suite:

	build	tests
UE 5.7	Succeeded, 0 errors, 0 warnings	59/59
UE 5.8.1	Succeeded, 0 errors, 0 warnings	59/59

Each engine was wiped and rebuilt rather than reusing the other's output, confirmed by the BuildId in UnrealEditor.modules changing (5.7 47537391, 5.8 55116800).

One run hit the known StreamChat.ChatApi.Channel flake (Expected 'Channel muted' to be true, an eventual-consistency assertion in that block's shared LatentBeforeEach, unrelated to anything in this release). Two clean 59/59 runs followed.

Note for the release process

initiate_release.yml could not do this itself: its permissions: block grants contents: read, so pushing the release branch fails with Permission to GetStream/stream-chat-unreal.git denied to github-actions[bot] (403). The bump and commit succeed, only the push is denied. See run 31398622527. This branch was therefore prepared with the same steps run locally. Worth fixing the workflow to contents: write separately.

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