Slash command inside a paragraph tag in rich text editor does not work in the timeline

[alunturner]

In the rich text editor, we start out with an empty composer. If the user inserts a new paragraph, then removes a paragraph, although the composer looks empty, it in fact contains a single p tag. This changes the output in the message body as shown.

steps	model
start composer	""
insert command	"/sample_command"
remove all text	""
insert a paragraph	"<p>&nbsp;</p><p>&nbsp;</p>"
remove a paragraph	"<p>&nbsp;</p>"
insert command	"<p>/sample_command</p>"

This means that if a user sends a slash command after these steps, it is incorrectly recognised (due to the opening of the p tag) and incorrectly processed. The slash commands seems to be designed to work with a string of text arguments after the command, so we could simply strip the opening and closing p tags from a message before we send it.

This could also potentially be rolled into the task #679, as we could simply output a raw text string if the rust model detects that the message starts with a command. I think this would be the neatest solution.