[keyserver/web] Enable announcement subchannel creation

Summary: While working on [[https://linear.app/comm/issue/ENG-5182 | ENG-5182]], I noticed that we prevent subchannel creation to be announcement channels. From an initial investigation, it looks like it's been disabled since [[ https://phab.comm.dev/D5211 | D5211 ]]. An error is thrown when attempting to create a new subchannel with the announcement setting because it fails the [[ https://github.com/CommE2E/comm/blob/ce4e185558c1a5af773a4291a44b0c6c19c88fcf/keyserver/src/responders/thread-responders.js#L169-L186 | input validation ]].

Test Plan: Ran `yarn workspace lib test` (to make sure `thread-responders.test.js` still worked, and more importantly manually tested creating both an open announcement subchannel and a secret announcement subchannel. The permissions like I mentioned are kind of weird though since non-members of the new secret subchannel can discover it in the navigation drawer, so I'll make it part of my overall permissions fixes for ENG-5182.

Reviewers: atul, ginsu, michal, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9489

keyserver/src/responders/thread-responders.js

@@ -180,6 +180,8 @@ const newThreadRequestInputValidator: TUnion<ServerNewThreadRequest> = t.union([
       threadTypes.LOCAL,
       threadTypes.COMMUNITY_ROOT,
       threadTypes.COMMUNITY_ANNOUNCEMENT_ROOT,
+      threadTypes.COMMUNITY_OPEN_ANNOUNCEMENT_SUBTHREAD,
+      threadTypes.COMMUNITY_SECRET_ANNOUNCEMENT_SUBTHREAD,
     ]),
     ...threadRequestValidationShape,
   }),

web/modals/threads/create/compose-subchannel-modal.react.js

@@ -99,12 +99,7 @@ function ComposeSubchannelModal(props: Props): React.Node {
 
       return result;
     } catch (e) {
-      await setErrorMessage(
-        e.message === 'invalid_parameters' && announcement
-          ? 'announcement channels currently not available'
-          : 'unknown error',
-      );
-
+      await setErrorMessage('unknown error');
       return null;
     }
   }, [