Prevent user from submitting declaration until mandatory fields are filled

[makelicious]

Description

This ticket is to introduce the basic mechanism for controlling the submit button of the review page based on the completeness of the form. More on "who sees what text and performs which action" in this ticket.

1. If the form is incomplete and you have the scope record.declaration-submit-incomplete, you should see

2. If the form is incomplete and you do not have the scope, you see

3. If the form is complete

[makelicious]

ping markus before starting this one @tareq89

[makelicious]

Better to work on the other items first

[makelicious]

@rikukissa will update the actual scope