Use email fields for feedback form

Otherwise we can end up collecting invalid email addresses…

This required some refactoring to allow our email fields to be optional
(but not by default).

tests/app/main/views/test_feedback.py

@@ -17,6 +17,7 @@ from tests.conftest import (
     mock_get_services,
     mock_get_services_with_no_services,
     mock_get_services_with_one_service,
+    normalize_spaces,
 )
 
 
@@ -224,6 +225,30 @@ def test_email_address_required_for_problems(
     assert isinstance(page.find('span', {'class': 'error-message'}), expected_error)
 
 
+@freeze_time('2016-12-12 12:00:00.000000')
+@pytest.mark.parametrize('ticket_type', (
+    PROBLEM_TICKET_TYPE, QUESTION_TICKET_TYPE
+))
+def test_email_address_must_be_valid_if_provided_to_support_form(
+    client,
+    mocker,
+    ticket_type,
+):
+    response = client.post(
+        url_for('main.feedback', ticket_type=ticket_type),
+        data={
+            'feedback': 'blah',
+            'email_address': 'not valid',
+        },
+    )
+    assert response.status_code == 200
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+
+    assert normalize_spaces(page.select_one('span.error-message').text) == (
+        'Enter a valid email address'
+    )
+
+
 @pytest.mark.parametrize('ticket_type, severe, is_in_business_hours, is_urgent, is_p1', [
 
     # business hours, always urgent, never p1