Fix

Add email signup screen as described in #7139. The new SignupMagicLinkFragment class is similar to the LoginMagicLinkSentFragment class, but not entirely. We can create a BaseMagicLinkFragment class to help abstract common code as an optimization when we move the signup code into the WordPressLoginFlow library. I chose not to do that at this time to avoid conflicts with ongoing development.

Test

0. Clear app data.
1. Tap Sign Up button.
2. Tap Sign Up with Email button.
3. Enter email address not associated with WordPress.com account.
4. Notice Signup Magic Link screen.
5. Check email inbox of address used in Step 3.
6. Notice signup email from WordPress.com.
7. Tap Try Again button.
8. Check email inbox of address used in Step 3.
9. Notice another signup email from WordPress.com.

Note

These changes do not include handling interception of the magic link from the signup email. That will be covered in the subsequent epilogue issue.