[keyserver] Show the most recent thread when opening the web app without providing a thread ID
Summary:
The most recent thread can be thick and the keyserver doesn't know about it. In this case we can rely on the app to compute the activeChatThreadID instead of the keyserver. In validateStateAndQueueOpsProcessing we're handling an empty state.navInfo.activeChatThreadID by calling mostRecentlyReadThreadSelector. This means that we can simply stop handling empty activeChatThreadID on the keyserver side.
Test Plan:
Made sure that the most recent thread is thick. Opened /webapp and /webapp/chat and verified that the most recent thread is shown.
Updated the state so that a thin thread is the most recent and performed the same test.
Made sure that opening a link to a thin and to a thick thread still opens it even if it isn't the most recent.
Reviewers: kamil, inka
Reviewed By: inka
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D13590