Do not insert trailing colon after mention/pill if cursor is in the middle of a message

[MadLittleMods]

Is your suggestion related to a problem? Please describe.

When mentioning a user by clicking their name to autofill the mention or using the user typeahead, there is always a trailing colon(:) after the mention/pill which doesn't fit right in the middle of a sentence.

Describe the solution you'd like

Do not insert trailing colon after mention/pill if your cursor is in the middle of a message.

The trailing colon seems fine for the start of a message or new line but doesn't seem correct to use it in the middle of a sentence/message.

Describe alternatives you've considered

Alternatives could be not inserting a colon at all.

For reference on Gitter, we just insert the @mention plus a space after.

Additional context

I'm making this issue while thinking about https://gitlab.com/gitterHQ/webapp/-/issues/2654 but I am not suggesting this is a fix for that issue.

Related issues:

• Pills don't have a suffixed colon anymore #7033
• CIDER: Colon after pill is missing #11563
• Inserting a mention at start of line in new composer should prepend <COLON>:<SPACE> as with auto complete #10719
• Remove ':' on mention inserts #16682
• CIDER