Retrieve domain invitations on first login

src/djangooidc/backends.py

@@ -49,6 +49,8 @@ class OpenIdConnectBackend(ModelBackend):
             user, created = UserModel.objects.update_or_create(**args)
             if created:
                 user = self.configure_user(user, **kwargs)
+                # run a newly created user's callback for a first-time login
+                user.first_login()
         else:
             try:
                 user = UserModel.objects.get_by_natural_key(username)

src/registrar/models/user.py

@@ -1,6 +1,8 @@
 from django.contrib.auth.models import AbstractUser
 from django.db import models
 
+from .domain_invitation import DomainInvitation
+
 from phonenumber_field.modelfields import PhoneNumberField  # type: ignore
 
 
@@ -31,3 +33,14 @@ class User(AbstractUser):
             return self.email
         else:
             return self.username
+
+    def first_login(self):
+        """Callback when the user is authenticated for the very first time.
+
+        When a user first arrives on the site, we need to retrieve any domain
+        invitations that match their email address.
+        """
+        for invitation in DomainInvitation.objects.filter(
+            email=self.email, status=DomainInvitation.SENT
+        ):
+            invitation.retrieve()

src/registrar/tests/test_models.py

@@ -193,6 +193,11 @@ class TestInvitations(TestCase):
         with self.assertRaises(RuntimeError):
             self.invitation.retrieve()
 
+    def test_retrieve_on_first_login(self):
+        """A new user's first_login callback retrieves their invitations."""
+        self.user.first_login()
+        self.assertTrue(UserDomainRole.objects.get(user=self.user, domain=self.domain))
+
 
 @skip("Not implemented yet.")
 class TestDomainApplicationLifeCycle(TestCase):

src/registrar/tests/test_views.py

@@ -1196,3 +1196,28 @@ class TestDomainDetail(TestWithDomainPermissions, WebTest):
         self.client.post(reverse("invitation-delete", kwargs={"pk": invitation.id}))
         with self.assertRaises(DomainInvitation.DoesNotExist):
             DomainInvitation.objects.get(id=invitation.id)
+
+    @boto3_mocking.patching
+    def test_domain_invitation_flow(self):
+        """Send an invitation to a new user, log in and load the dashboard."""
+        EMAIL = "mayor@igorville.gov"
+        User.objects.filter(email=EMAIL).delete()
+
+        add_page = self.app.get(
+            reverse("domain-users-add", kwargs={"pk": self.domain.id})
+        )
+        session_id = self.app.cookies[settings.SESSION_COOKIE_NAME]
+        add_page.form["email"] = EMAIL
+        self.app.set_cookie(settings.SESSION_COOKIE_NAME, session_id)
+        add_page.form.submit()
+
+        # user was invited, create them
+        new_user = User.objects.create(username=EMAIL, email=EMAIL)
+        # log them in to `self.app`
+        self.app.set_user(new_user.username)
+        # and manually call the first login callback
+        new_user.first_login()
+
+        # Now load the home page and make sure our domain appears there
+        home_page = self.app.get(reverse("home"))
+        self.assertContains(home_page, self.domain.name)