✨(mailboxes) add mail provisioning api integration

We want people to create new mailboxes in La Régie.
This commit adds integration with intermediary dimail-api,
which will in turn send our email creation request to Open-Xchange.

src/backend/mailbox_manager/utils/dimail.py

@@ -0,0 +1,88 @@
+"""A minimalist client to synchronize with mailbox provisioning API."""
+
+from logging import getLogger
+
+from django.conf import settings
+from django.core import exceptions
+
+import requests
+from rest_framework import status
+from urllib3.util import Retry
+
+logger = getLogger(__name__)
+
+adapter = requests.adapters.HTTPAdapter(
+    max_retries=Retry(
+        total=4,
+        backoff_factor=0.1,
+        status_forcelist=[500, 502],
+        allowed_methods=["PATCH"],
+    )
+)
+
+session = requests.Session()
+session.mount("http://", adapter)
+session.mount("https://", adapter)
+
+
+class DimailAPIClient:
+    """A dimail-API client."""
+
+    def get_headers(self, domain):
+        """Build header dict from domain object."""
+        # self.secret is the encoded basic auth, to request a new token from dimail-api
+        headers = {"Content-Type": "application/json"}
+
+        response = requests.get(
+            f"{settings.MAIL_PROVISIONING_API_URL}/token/",
+            headers={"Authorization": f"Basic {domain.secret}"},
+            timeout=status.HTTP_200_OK,
+        )
+
+        if response.json() == "{'detail': 'Permission denied'}":
+            raise exceptions.PermissionDenied(
+                "This secret does not allow for a new token."
+            )
+
+        if "access_token" in response.json():
+            headers["Authorization"] = f"Bearer {response.json()['access_token']}"
+
+        return headers
+
+    def send_mailbox_request(self, mailbox):
+        """Send a CREATE mailbox request to mail provisioning API."""
+
+        payload = {
+            "email": f"{mailbox.local_part}@{mailbox.domain}",
+            "givenName": mailbox.first_name,
+            "surName": mailbox.last_name,
+            "displayName": f"{mailbox.first_name} {mailbox.last_name}",
+        }
+
+        try:
+            response = session.post(
+                f"{settings.MAIL_PROVISIONING_API_URL}/domains/{mailbox.domain}/mailboxes/",
+                json=payload,
+                headers=self.get_headers(mailbox.domain),
+                verify=True,
+                timeout=10,
+            )
+        except requests.exceptions.ConnectionError as e:
+            logger.error(
+                "Connection error while trying to reach %s.",
+                settings.MAIL_PROVISIONING_API_URL,
+                exc_info=e,
+            )
+
+        if response.status_code == status.HTTP_201_CREATED:
+            extra = {"response": response.content.decode("utf-8")}
+            # This a temporary broken solution. Password will soon be sent
+            # from OX servers but their prod is not ready.
+            # In the meantime, we log mailbox info (including password !)
+            logger.info(
+                "Mailbox successfully created on domain %s",
+                mailbox.domain.name,
+                extra=extra,
+            )
+
+        return response