Allow use of `e` from Message information popup

[neiljp]

In the web app, i e shows one of the following in the drop-down menu following pressing i:

• View message source
• Edit message

This depends upon the editing rights of the user, which can vary with time.

Within ZT, users can already press e on a given message to edit it, if they are able. However, coming from the web app, i e would give hotkey parity/compatibility.

For ZT, we currently use r for allowing showing the "raw" message, ie. i r, which shows the scrollable markdown source in a popup.

Proposal:

• [ ] If the user can edit the message, show this as a separate action under 'Viewing Actions' (possibly renamed to 'Actions'?); this would close the popup and go to the compose/edit state.
• [ ] if the user cannot edit the message, include e under the r list of keys; this should then trigger the same action as r.

There are various factors motivating this approach:

• We don't currently support simply showing a 'raw' message (ie. in markdown) in the compose box, if we can't edit it - and similarly the web app shows messages in the message feed instead
• Our r view gives the greatest scope for showing more of a message in a scrollable state, so if it's not editable, or if the user just wants to view the message, this is cleaner

Implementing this will depend upon a reliable 'can user edit topic' method, which is close to readiness via #1235.

[zulipbot]

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

[rsashank]

@zulipbot claim

[zulipbot]

Hello @rsashank!

Thanks for your interest in Zulip! You have attempted to claim an issue without the label "help wanted". You can only claim and submit pull requests for issues with the help wanted label.

If this is your first time here, we recommend reading our guide for new contributors before getting started.