💚(ci) call the Dimail container by its actual name (and port)

So that E2E tests in Github Actions can connect to Dimail container.
Previously we were attempting to connect as if from the outside. But
the E2E process is in fact inside the Docker Compose network.
("The tests came from inside the house !")
https://tvtropes.org/pmwiki/pmwiki.php/Main/TheCallsAreComingFromInsideTheHouse

src/backend/mailbox_manager/management/commands/setup_dimail_db.py

@@ -13,7 +13,7 @@ from mailbox_manager.models import MailDomain
 User = get_user_model()
 
 
-DIMAIL_URL = "http://host.docker.internal:8001"
+DIMAIL_URL = "http://dimail:8000"
 admin = {"username": "admin", "password": "admin"}
 regie = {"username": "la_regie", "password": "password"}
 

src/backend/people/settings.py

@@ -432,7 +432,7 @@ class Base(Configuration):
         environ_prefix=None,
     )
     MAIL_PROVISIONING_API_URL = values.Value(
-        default="http://host.docker.internal:8001",
+        default="http://dimail:8000",
         environ_name="MAIL_PROVISIONING_API_URL",
         environ_prefix=None,
     )

src/helm/env.d/dev/values.desk.yaml.gotmpl

@@ -52,7 +52,7 @@ backend:
     POSTGRES_PASSWORD: pass
     REDIS_URL: redis://default:pass@redis-master:6379/1
     WEBMAIL_URL: "https://onestendev.yapasdewebmail.fr"
-    MAIL_PROVISIONING_API_URL: "http://host.docker.internal:8001"
+    MAIL_PROVISIONING_API_URL: "http://dimail:8000"
     MAIL_PROVISIONING_API_CREDENTIALS:
       secretKeyRef:
         name: backend