Add autocomplete to email address on register form

GOV.UK Design System recommends:
> You should also set the autocomplete attribute to email. This lets
> browsers autofill the email address on a user’s behalf if they’ve
> entered it previously.

Only doing this on the register and sign in forms because it’s unlikely
to be helpful where a user is trying to enter someone else’s email
address.

app/templates/views/register.html

@@ -14,7 +14,7 @@ Create an account
     <h1 class="heading-large">Create an account</h1>
     {% call form_wrapper(autocomplete=True) %}
       {{ textbox(form.name, width='3-4') }}
-      {{ textbox(form.email_address, hint="Must be from a government organisation", width='3-4', safe_error_message=True) }}
+      {{ textbox(form.email_address, hint="Must be from a government organisation", width='3-4', safe_error_message=True, autocomplete='email') }}
       <div class="extra-tracking">
         {{ textbox(form.mobile_number, width='3-4', hint='We’ll send you a security code by text message') }}
       </div>

app/templates/views/signin.html

@@ -32,7 +32,7 @@
     {% endif %}
 
     {% call form_wrapper(autocomplete=True) %}
-      {{ textbox(form.email_address) }}
+      {{ textbox(form.email_address, autocomplete='email') }}
       {{ textbox(form.password) }}
       {{ page_footer("Continue", secondary_link=url_for('.forgot_password'), secondary_link_text="Forgot your password?") }}
     {% endcall %}

tests/app/main/views/test_manage_users.py

@@ -387,6 +387,16 @@ def test_invite_user_allows_to_choose_auth(
     assert sms_auth_radio_button.has_attr("disabled") is False
 
 
+def test_invite_user_has_correct_email_field(
+    client_request,
+    mock_get_users_by_service,
+    mock_get_template_folders,
+):
+    email_field = client_request.get('main.invite_user', service_id=SERVICE_ONE_ID).select_one('#email_address')
+    assert email_field['spellcheck'] == 'false'
+    assert 'autocomplete' not in email_field
+
+
 def test_should_not_show_page_for_non_team_member(
     client_request,
     mock_get_users_by_service,

tests/app/main/views/test_register.py

@@ -16,6 +16,7 @@ def test_render_register_returns_template_with_form(client):
     page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
     assert page.find('input', attrs={'name': 'auth_type'}).attrs['value'] == 'sms_auth'
     assert page.select_one('#email_address')['spellcheck'] == 'false'
+    assert page.select_one('#email_address')['autocomplete'] == 'email'
     assert 'Create an account' in response.get_data(as_text=True)