🚸(backend) use unaccented full name for user search

We have the user full name through OIDC in the database, but the search only
used the email field.
This change allows to search for a user by their first and/or
last name (fix #929).
Given that user names are more likely than emails to include diacritics, it
unaccents both the query and the database entry for search (fix #1091).
It also unaccents for email so that internationalized domain names are
managed whether or not the accent is included in the search.
An unaccented gin index is added on users full_name an email fields.
Using a manual migration because a wrapper around unaccent is necessary
to make it IMMUTABLE (cf.
https://stackoverflow.com/questions/9063402/ )

src/backend/core/tests/test_api_users.py

@@ -76,6 +76,131 @@ def test_api_users_list_query_email():
     assert user_ids == []
 
 
+def test_api_users_list_query_email_with_internationalized_domain_names():
+    """
+    Authenticated users should be able to list users and filter by email.
+    It should work even if the email address contains an internationalized domain name.
+    """
+    user = factories.UserFactory()
+
+    client = APIClient()
+    client.force_login(user)
+
+    jean = factories.UserFactory(email="jean.martin@éducation.fr")
+    marie = factories.UserFactory(email="marie.durand@education.fr")
+    kurokawa = factories.UserFactory(email="contact@黒川.日本")
+
+    response = client.get("/api/v1.0/users/?q=jean.martin@education.fr")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(jean.id)]
+
+    response = client.get("/api/v1.0/users/?q=jean.martin@éducation.fr")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(jean.id)]
+
+    response = client.get("/api/v1.0/users/?q=marie.durand@education.fr")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(marie.id)]
+
+    response = client.get("/api/v1.0/users/?q=marie.durand@éducation.fr")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(marie.id)]
+
+    response = client.get("/api/v1.0/users/?q=contact@黒川.日本")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(kurokawa.id)]
+
+
+def test_api_users_list_query_full_name():
+    """
+    Authenticated users should be able to list users and filter by full name.
+    Only results with a Trigram similarity greater than 0.2 with the query should be returned.
+    """
+    user = factories.UserFactory()
+
+    client = APIClient()
+    client.force_login(user)
+
+    dave = factories.UserFactory(email="contact@work.com", full_name="David Bowman")
+
+    response = client.get(
+        "/api/v1.0/users/?q=David",
+    )
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(dave.id)]
+
+    response = client.get("/api/v1.0/users/?q=Bowman")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(dave.id)]
+
+    response = client.get("/api/v1.0/users/?q=bowman")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(dave.id)]
+
+    response = client.get("/api/v1.0/users/?q=BOWMAN")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(dave.id)]
+
+    response = client.get("/api/v1.0/users/?q=BoWmAn")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(dave.id)]
+
+    response = client.get("/api/v1.0/users/?q=Bovin")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == []
+
+
+def test_api_users_list_query_accented_full_name():
+    """
+    Authenticated users should be able to list users and filter by full name with accents.
+    Only results with a Trigram similarity greater than 0.2 with the query should be returned.
+    """
+    user = factories.UserFactory()
+
+    client = APIClient()
+    client.force_login(user)
+
+    fred = factories.UserFactory(
+        email="contact@work.com", full_name="Frédérique Lefèvre"
+    )
+
+    response = client.get("/api/v1.0/users/?q=Frédérique")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(fred.id)]
+
+    response = client.get("/api/v1.0/users/?q=Frederique")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(fred.id)]
+
+    response = client.get("/api/v1.0/users/?q=Lefèvre")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(fred.id)]
+
+    response = client.get("/api/v1.0/users/?q=Lefevre")
+    assert response.status_code == 200
+    user_ids = [user["id"] for user in response.json()]
+    assert user_ids == [str(fred.id)]
+
+    response = client.get("/api/v1.0/users/?q=François Lorfebvre")
+    assert response.status_code == 200
+    users = [user["full_name"] for user in response.json()]
+    assert users == []
+
+
 def test_api_users_list_limit(settings):
     """
     Authenticated users should be able to list users and the number of results