Set from field on user messaging emails correctly

[sebgrebe]

• Some providers were bouncing emails from user to other emails because the "from" field was incorrectly set
• This MR fixes this and expands messaging unit test to test this
• Where a group has multiple organisers, sends to first alphabetical one
• Refactors group messaging view to have same pattern as profiles' and adds unit tests
• Removes toggling of group messaging via messaging flag