Save message editable content as well

[diego3g]

Today we only save the message content in HTML format when the user creates it, but this prevents us from updating that message before sending it as the HTML is not editable by DraftJS on front-end.

We should save the message content in Draft format until the message is sent.

When the message is sent, we should fill another column inside the messages table like finalBody or finalContent that will have the message final HTML so we don't lose track about the message content in Draft format.