fix(teams): Keep a team's issue subscriptions when removing a pending invite

Removing a member from a team unsubscribes them from the team's issues with
GroupSubscription.filter(user_id=member.user_id). A pending invite has no
user, so user_id=None matched the team's own subscriptions (user_id is NULL on
those rows) and deleted them.

Author: gricha

src/sentry/core/endpoints/organization_member_team_details.py

@@ -586,6 +586,9 @@ def _unsubscribe_issues(team: Team, member: OrganizationMember) -> None:
         """
         Unsubscribe user from issues the team is subscribed to
         """
+        # A pending invite has no subscriptions, and user_id=None would match the team's own.
+        if member.user_id is None:
+            return
         team_assigned_groups = GroupAssignee.objects.filter(team_id=team.id).values_list(
             "group_id", flat=True
         )

tests/sentry/core/endpoints/test_organization_member_team_details.py

@@ -800,6 +800,26 @@ def test_cannot_leave_idp_provisioned_team(self) -> None:
             team=idp_team, organizationmember=member
         ).exists()
 
+    def test_removing_pending_invite_keeps_team_subscriptions(self) -> None:
+        invite = self.create_member(
+            organization=self.org, email="invited@example.com", role="member", teams=[self.team]
+        )
+        group = self.create_group()
+        GroupAssignee.objects.create(group=group, team=self.team, project=group.project)
+        GroupSubscription.objects.create(
+            group=group,
+            project=group.project,
+            team=self.team,
+            reason=GroupSubscriptionReason.assigned,
+        )
+
+        self.login_as(self.user)
+        self.get_success_response(
+            self.org.slug, invite.id, self.team.slug, status_code=status.HTTP_200_OK
+        )
+
+        assert GroupSubscription.objects.filter(group=group, team=self.team).exists()
+
     def test_unsubscribe_user_from_team_issues_legacy(self) -> None:
         """
         We have some legacy DB rows from before the GroupSubscription table had a team_id