restrict emoji reaction to administrators in announcement streams

[ghost]

From this conversation: https://chat.zulip.org/#narrow/stream/137-feedback/topic/selectively.20restrict.20emoji.20reactions

For announcement streams, it should be possible to prevent of emoji reactions from non-administrator users. The toggle should be optional, ideally at a stream level, but at least at a global level, so that organizations can opt into this behavior if desired.

The catch is to convey to users that emoji reactions are intentionally not allowed (and not that anything is broken). In the chat, we suggested having the emoji reaction smiley face with a line through it may be sufficient.

It's unclear if this behavior should be extended outside of announcement streams, but perhaps it's best to just start with announcement streams and extend it only if requested.

[zulipbot]

Hello @zulip/server-streams members, this issue was labeled with the "area: stream settings" label, so you may want to check it out!

[sahil839]

@zulipbot claim

[zulipbot]

Hello @sahil839, you have been unassigned from this issue because you have not updated this issue or any referenced pull requests for over 14 days.

You can reclaim this issue or claim any other issue by commenting @zulipbot claim on that issue.

Thanks for your contributions, and hope to see you again soon!

[sahil839]

@zulipbot I am currently working on this issue.

[sahil839]

@zulipbot claim

[zulipbot]

Hello @sahil839, you have been unassigned from this issue because you have not updated this issue or any referenced pull requests for over 14 days.

You can reclaim this issue or claim any other issue by commenting @zulipbot claim on that issue.

Thanks for your contributions, and hope to see you again soon!

[timabbott]

This issue should be implemented after #19525, since we'll want to use the framework described there to make "who can react" a user group.