Let users on email auth delete their mobile numbers

Sometimes users ask us to delete their mobile numbers for them.

If those users are on email auth, they should be able to
delete their number themselves.

This will save them writing a support ticket and save us
going into the database.

tests/app/main/views/test_user_profile.py

@@ -183,6 +183,59 @@ def test_should_show_mobile_number_page(
 ):
     page = client_request.get(('main.user_profile_mobile_number'))
     assert 'Change your mobile number' in page.text
+    assert 'Delete your number' not in page.text
+
+
+def test_change_your_mobile_number_page_shows_delete_link_if_user_on_email_auth(
+    client_request,
+    api_user_active_email_auth,
+    mocker
+):
+    mocker.patch('app.user_api_client.get_user', return_value=api_user_active_email_auth)
+    page = client_request.get(('main.user_profile_mobile_number'))
+    assert 'Change your mobile number' in page.text
+    assert 'Delete your number' in page.text
+
+
+def test_confirm_delete_mobile_number(
+    client_request,
+    api_user_active_email_auth,
+    mocker
+):
+    mocker.patch('app.user_api_client.get_user', return_value=api_user_active_email_auth)
+
+    page = client_request.get(
+        '.user_profile_confirm_delete_mobile_number',
+        _test_page_title=False,
+    )
+
+    assert normalize_spaces(page.select_one('.banner-dangerous').text) == (
+        'Are you sure you want to delete your mobile number from Notify? '
+        'Yes, delete'
+    )
+    assert 'action' not in page.select_one('.banner-dangerous form')
+    assert page.select_one('.banner-dangerous form')['method'] == 'post'
+
+
+def test_delete_mobile_number(
+    client_request,
+    api_user_active_email_auth,
+    mocker
+):
+    mocker.patch('app.user_api_client.get_user', return_value=api_user_active_email_auth)
+    mock_delete = mocker.patch('app.user_api_client.update_user_attribute')
+
+    client_request.post(
+        '.user_profile_mobile_number_delete',
+        _expected_redirect=url_for(
+            '.user_profile',
+            _external=True,
+        )
+    )
+    mock_delete.assert_called_once_with(
+        api_user_active_email_auth["id"],
+        mobile_number=None
+    )
 
 
 @pytest.mark.parametrize('phone_number_to_register_with', [