Make user API client return JSON, not a model

The data flow of other bits of our application looks like this:
```
                         API (returns JSON)
                                  ⬇
          API client (returns a built in type, usually `dict`)
                                  ⬇
          Model (returns an instance, eg of type `Service`)
                                  ⬇
                         View (returns HTML)
```
The user API client was architected weirdly, in that it returned a model
directly, like this:

```
                         API (returns JSON)
                                  ⬇
    API client (returns a model, of type `User`, `InvitedUser`, etc)
                                  ⬇
                         View (returns HTML)
```

This mixing of different layers of the application is bad because it
makes it hard to write model code that doesn’t have circular
dependencies. As our application gets more complicated we will be
relying more on models to manage this complexity, so we should make it
easy, not hard to write them.

It also means that most of our mocking was of the User model, not just
the underlying JSON. So it would have been easy to introduce subtle bugs
to the user model, because it wasn’t being comprehensively tested. A lot
of the changed lines of code in this commit mean changing the tests to
mock only the JSON, which means that the model layer gets implicitly
tested.

For those reasons this commit changes the user API client to return
JSON, not an instance of `User` or other models.

tests/app/main/views/test_new_password.py

@@ -16,7 +16,7 @@ def test_should_render_new_password_template(
     mock_send_verify_code,
     mock_get_user_by_email_request_password_reset,
 ):
-    data = json.dumps({'email': api_user_active.email_address, 'created_at': str(datetime.utcnow())})
+    data = json.dumps({'email': api_user_active['email_address'], 'created_at': str(datetime.utcnow())})
     token = generate_token(data, app_.config['SECRET_KEY'],
                            app_.config['DANGEROUS_SALT'])
 
@@ -45,13 +45,13 @@ def test_should_redirect_to_two_factor_when_password_reset_is_successful(
     mock_reset_failed_login_count
 ):
     user = mock_get_user_by_email_request_password_reset.return_value
-    data = json.dumps({'email': user.email_address, 'created_at': str(datetime.utcnow())})
+    data = json.dumps({'email': user['email_address'], 'created_at': str(datetime.utcnow())})
     token = generate_token(data, app_.config['SECRET_KEY'], app_.config['DANGEROUS_SALT'])
     response = client.post(url_for_endpoint_with_token('.new_password', token=token),
                            data={'new_password': 'a-new_password'})
     assert response.status_code == 302
     assert response.location == url_for('.two_factor', _external=True)
-    mock_get_user_by_email_request_password_reset.assert_called_once_with(user.email_address)
+    mock_get_user_by_email_request_password_reset.assert_called_once_with(user['email_address'])
 
 
 def test_should_redirect_index_if_user_has_already_changed_password(
@@ -63,13 +63,13 @@ def test_should_redirect_index_if_user_has_already_changed_password(
     mock_reset_failed_login_count
 ):
     user = mock_get_user_by_email_user_changed_password.return_value
-    data = json.dumps({'email': user.email_address, 'created_at': str(datetime.utcnow())})
+    data = json.dumps({'email': user['email_address'], 'created_at': str(datetime.utcnow())})
     token = generate_token(data, app_.config['SECRET_KEY'], app_.config['DANGEROUS_SALT'])
     response = client.post(url_for_endpoint_with_token('.new_password', token=token),
                            data={'new_password': 'a-new_password'})
     assert response.status_code == 302
     assert response.location == url_for('.index', _external=True)
-    mock_get_user_by_email_user_changed_password.assert_called_once_with(user.email_address)
+    mock_get_user_by_email_user_changed_password.assert_called_once_with(user['email_address'])
 
 
 def test_should_redirect_to_forgot_password_with_flash_message_when_token_is_expired(
@@ -98,8 +98,8 @@ def test_should_sign_in_when_password_reset_is_successful_for_email_auth(
     mock_update_user_password
 ):
     user = mock_get_user_by_email_request_password_reset.return_value
-    user.auth_type = 'email_auth'
-    data = json.dumps({'email': user.email_address, 'created_at': str(datetime.utcnow())})
+    user['auth_type'] = 'email_auth'
+    data = json.dumps({'email': user['email_address'], 'created_at': str(datetime.utcnow())})
     token = generate_token(data, app_.config['SECRET_KEY'], app_.config['DANGEROUS_SALT'])
 
     response = client.post(url_for_endpoint_with_token('.new_password', token=token),
@@ -111,7 +111,7 @@ def test_should_sign_in_when_password_reset_is_successful_for_email_auth(
     assert mock_reset_failed_login_count.called
 
     # the log-in flow makes a couple of calls
-    mock_get_user.assert_called_once_with(user.id)
-    mock_update_user_password.assert_called_once_with(user.id, password='a-new_password')
+    mock_get_user.assert_called_once_with(user['id'])
+    mock_update_user_password.assert_called_once_with(user['id'], 'a-new_password')
 
     assert not mock_send_verify_code.called