🐛(backend) submit for signature handle timeout delete signing procedure

When the method `submit_for_signature` needs to delete a signing procedure
because some elements have changed overtime in the contract definition
and before the student signed the document, it appears that it may take
a while on the signature provider side to execute the deletion.
In order to handle and update our contract, we have added a try
except block to catch the timeout issue, and proceed to update the contract
as if we would have received the response from the signature provider.
Before we added the fix, the contract would keep the old reference that would
not work when the student wanted to sign the document, causing another error
because it has already been deleted after the timeout we have set in the
signature backend. In some cases, due to the timeout error, when we attempt
to delete the outdated reference, we would then have a NOT_FOUND status
code, we should also reset the contrat submission value as well to restart with
a new contrat to submit.

src/backend/joanie/core/exceptions.py

@@ -2,6 +2,8 @@
 Specific exceptions for the core application
 """
 
+from requests.exceptions import ReadTimeout
+
 
 class EnrollmentError(Exception):
     """An exception to raise if an enrollment fails."""
@@ -29,3 +31,10 @@ class CertificateGenerationError(Exception):
     Exception raised when the certificate generation process fails due to the order not meeting
     all specified conditions.
     """
+
+
+class BackendTimeOut(ReadTimeout):
+    """
+    Exception raised when a backend reaches the timeout set when we are waiting
+    for the response.
+    """

src/backend/joanie/core/models/products.py

@@ -18,7 +18,7 @@
 from urllib3.util import Retry
 
 from joanie.core import enums
-from joanie.core.exceptions import CertificateGenerationError
+from joanie.core.exceptions import BackendTimeOut, CertificateGenerationError
 from joanie.core.fields.schedule import OrderPaymentScheduleEncoder
 from joanie.core.flows.order import OrderFlow
 from joanie.core.models.accounts import User
@@ -37,7 +37,9 @@
 from joanie.core.utils import contract_definition as contract_definition_utility
 from joanie.core.utils import issuers, webhooks
 from joanie.core.utils.payment_schedule import generate as generate_payment_schedule
+from joanie.core.utils.signature import handle_signature_deletion_error
 from joanie.signature.backends import get_signature_backend
+from joanie.signature.exceptions import DeleteSignatureProcedureFailed
 
 logger = logging.getLogger(__name__)
 
@@ -965,9 +967,25 @@ def submit_for_signature(self, user: User):
         )
 
         if should_be_resubmitted:
-            backend_signature.delete_signing_procedure(
-                contract.signature_backend_reference
-            )
+            # The signature provider may take some time to respond with the confirmation of the
+            # deletion. If we reach the timeout limit, we should reset the contract submission
+            # values because the signature provider will delete them.
+            # We won't be able to use the `contract.signature_backend_reference` again.
+            # There can be edge case where the signature backend reference was already deleted,
+            # causing an error that the reference was not found at the signature provider side.
+            try:
+                backend_signature.delete_signing_procedure(
+                    contract.signature_backend_reference
+                )
+            except BackendTimeOut as exception:  # pylint: disable=unused-variable
+                handle_signature_deletion_error(
+                    order=self, error_message="Timeout on signature reference deletion"
+                )
+            except DeleteSignatureProcedureFailed as exception:  # pylint: disable=unused-variable
+                handle_signature_deletion_error(
+                    order=self, error_message="Failed to delete signature procedure"
+                )
+            was_already_submitted = False
 
         # We want to submit or re-submit the contract for signature in three cases:
         # 1- the contract was never submitted for signature before

src/backend/joanie/core/utils/signature.py

@@ -4,11 +4,14 @@
 
 import hashlib
 import hmac
+import logging
 
 from django.conf import settings
 
 from rest_framework import exceptions
 
+logger = logging.getLogger(__name__)
+
 
 def check_signature(request, settings_name):
     """Check the signature of a request."""
@@ -33,3 +36,24 @@ def check_signature(request, settings_name):
     )
     if not signature_is_valid:
         raise exceptions.AuthenticationFailed("Invalid authentication.")
+
+
+def handle_signature_deletion_error(order, error_message):
+    """
+    Handles the exception raised on the deleting of signing procedure.
+    It's responsible to reset the submission values from the outdated
+    contract of the order.
+    """
+    logger.error(
+        error_message,
+        extra={
+            "context": {
+                "order": order.to_dict(),
+                "product": order.product.to_dict(),
+                "signature_backend_reference": (
+                    order.contract.signature_backend_reference
+                ),
+            }
+        },
+    )
+    order.contract.reset_submission_for_signature()