ensure emails are formatted before sending

we allow some invalid to addresses - for example, phone numbers with
spaces or brackets - in the database. This is so that users can match
up their data in a format that they expect (since they passed it in).
When we send SMS, we strip this formatting just before sending - but we
weren't with email. This commit changes that and adds some tests.

It also adds formatting for reply_to addresses. We should never expect
invalid reply_to email addresses in our data, but just in case, lets
validate them here.

Also, bump requirements.txt to capture some more email validation

tests/app/db.py

@@ -109,7 +109,7 @@ def create_notification(
     template,
     job=None,
     job_row_number=None,
-    to_field='+447700900855',
+    to_field=None,
     status='created',
     reference=None,
     created_at=None,
@@ -131,6 +131,9 @@ def create_notification(
     if created_at is None:
         created_at = datetime.utcnow()
 
+    if to_field is None:
+        to_field = '+447700900855' if template.template_type == SMS_TYPE else 'test@example.com'
+
     if status != 'created':
         sent_at = sent_at or datetime.utcnow()
         updated_at = updated_at or datetime.utcnow()