Send fxa_id, not email, in user basket sync

Salesforce already have FxA data so it's best not to send the email
as it would be duplicate info anyway. FxA is the source of truth for
emails.

docs/topics/basket.rst

@@ -36,10 +36,10 @@ User Accounts
     :<json int id: The numeric user id.
     :<json boolean deleted: Is the account deleted.
     :<json string|null display_name: The name chosen by the user.
-    :<json string email: Email address used by the user to login and create this account.
+    :<json string|null homepage: The user's website.
+    :<json string fxa_id|null: The user FxA Identifier
     :<json string|null last_login: The date of the last successful log in to the website.
     :<json string|null location: The location of the user.
-    :<json string|null homepage: The user's website.
 
 Add-ons
 ~~~~~~~
@@ -80,8 +80,8 @@ Here is an example of the full json that would be sent for an add-on:
             {
                 "id": 11263,
                 "deleted": false,
-                "display_name": "serses",
-                "email": "mozilla@virgule.net",
+                "display_name": "qwerty",
+                "fxa_id": "1209e9bf1eeb59d0934579b6db0ccad1",
                 "homepage": "",
                 "last_login": "2019-08-06T10:39:44Z",
                 "location": ""

src/olympia/accounts/serializers.py

@@ -265,6 +265,6 @@ class UserNotificationSerializer(serializers.Serializer):
 class UserProfileBasketSyncSerializer(UserProfileSerializer):
     class Meta(UserProfileSerializer.Meta):
         model = UserProfile
-        fields = ('id', 'deleted', 'display_name', 'email', 'homepage',
+        fields = ('id', 'deleted', 'display_name', 'homepage', 'fxa_id',
                   'last_login', 'location')
         read_only_fields = fields

src/olympia/accounts/tests/test_serializers.py

@@ -279,14 +279,15 @@ class TestUserProfileSerializer(TestPublicUserProfileSerializer,
 class TestUserProfileBasketSyncSerializer(TestCase):
     def setUp(self):
         self.user = user_factory(
-            display_name=None, last_login=self.days_ago(1))
+            display_name=None, last_login=self.days_ago(1),
+            fxa_id='qsdfghjklmù')
 
     def test_basic(self):
         serializer = UserProfileBasketSyncSerializer(self.user)
         assert serializer.data == {
             'deleted': False,
             'display_name': None,
-            'email': self.user.email,
+            'fxa_id': self.user.fxa_id,
             'homepage': '',
             'id': self.user.pk,
             'last_login': self.user.last_login.replace(
@@ -304,7 +305,7 @@ class TestUserProfileBasketSyncSerializer(TestCase):
         assert serializer.data == {
             'deleted': True,
             'display_name': None,
-            'email': None,
+            'fxa_id': None,
             'homepage': '',
             'id': self.user.pk,
             'last_login': self.user.last_login.replace(

src/olympia/addons/tests/test_serializers.py

@@ -1329,8 +1329,8 @@ class TestAddonBasketSyncSerializer(TestCase):
 
     def test_non_listed_author(self):
         self.addon = addon_factory()
-        user1 = user_factory()
-        user2 = user_factory()
+        user1 = user_factory(fxa_id='azerty')
+        user2 = user_factory(fxa_id=None)  # somehow no fxa_id.
         AddonUser.objects.create(
             addon=self.addon, user=user1, listed=True,
             role=amo.AUTHOR_ROLE_OWNER, position=1)
@@ -1342,7 +1342,7 @@ class TestAddonBasketSyncSerializer(TestCase):
             'id': user1.pk,
             'deleted': False,
             'display_name': '',
-            'email': user1.email,
+            'fxa_id': user1.fxa_id,
             'homepage': user1.homepage,
             'last_login': user1.last_login,
             'location': user1.location
@@ -1350,7 +1350,7 @@ class TestAddonBasketSyncSerializer(TestCase):
             'id': user2.pk,
             'deleted': False,
             'display_name': '',
-            'email': user2.email,
+            'fxa_id': user2.fxa_id,
             'homepage': user2.homepage,
             'last_login': user2.last_login,
             'location': user2.location

src/olympia/users/models.py

@@ -968,7 +968,7 @@ def watch_changes(old_attr=None, new_attr=None, instance=None,
             index_addons.delay(ids)
 
     basket_relevant_changes = (
-        'deleted', 'display_name', 'email', 'homepage', 'last_login',
+        'deleted', 'display_name', 'fxa_id', 'homepage', 'last_login',
         'location'
     )
     if any(field in changes for field in basket_relevant_changes):

src/olympia/users/tests/test_models.py

@@ -608,7 +608,7 @@ class TestUserProfile(TestCase):
         user = UserProfile.objects.get(id=4043307)
         # Note that basket_token is for newsletters, and is irrelevant here.
         user.update(
-            basket_token='FOO', fxa_id='BAR', is_public=True,
+            basket_token='FOO', email='newemail@example.com', is_public=True,
             read_dev_agreement=self.days_ago(42), notes='Blah',
             biography='Something', auth_id=12345)
         assert sync_object_to_basket_mock.delay.call_count == 0
@@ -628,6 +628,12 @@ class TestUserProfile(TestCase):
         assert sync_object_to_basket_mock.delay.called_with(
             'userprofile', 4043307)
 
+        sync_object_to_basket_mock.reset_mock()
+        user.update(fxa_id='wât')  # Can technically happen if admins do it.
+        assert sync_object_to_basket_mock.delay.call_count == 1
+        assert sync_object_to_basket_mock.delay.called_with(
+            'userprofile', 4043307)
+
     @mock.patch('olympia.amo.tasks.sync_object_to_basket')
     def test_user_deletion_synced_to_basket(
             self, sync_object_to_basket_mock):