Improve group update descriptions

[cascheberg]

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Description

• in conversation list: only show a short group update info (see conversation snippet gross on group update #2834)
• in group conversation: indicate which member updated the group, or "You ...", see screenshots

Before:

After:

// FREEBIE

Outgoing group update descriptions could be more precise if they didn't contain unchanged group title, members and avatar.

[moxie0]

This method is designed to be idempotent, and is called from several places. Instead of making it dependent on some external functionality (since it can now return an empty string), it seems both safer and cleaner to consider making your changes in this method.

[cascheberg]

I updated this PR in a followup commit. There is currently only that one caller, and it now passes the sender as a method parameter. Please let me know if you have suggestions other than these two approaches.

[RiseT]

Do you think it would be possible to differentiate between creating a group and editing/updating it? A message saying "You've updated the group" as confirmation for creating one feels a bit strange to me.

[moxie0]

in 3.32.0