Show snack bar when survey is completed

Show the message "Survey Complete" when a survey is completed.

To access a survey do the following:
- Create an account with the one of the three emails: handle2@test, handle3@test, handle4@test
- Restart app to get surveys (surveys are fetched during the splash screen)
- Click on "messages" button
- Click on one of the 3 accounts
- Look for a survey button
- Complete the survey
- After completion, you go back to the main message screen. The survey you just took is now gone, since you completed it. But it's hard to tell, so we need to add a snackbar that says "Survey Complete" once it's done