Save DepositRequest record before scheduling loading

_complete_deposit() schedules a loading task; but it was called before the
DepositRequest object was saved to the database.

This means that if the loading tasks executes very fast, or the DepositRequest
takes a while to save, then the loader won't see the current DepositRequest when
it queries the deposit's current state.

This is especially likely to happen with large code uploads, as saving them to
disk happens before the DepositRequest row is written to the database.

swh/deposit/api/common.py

-# Copyright (C) 2017-2022  The Software Heritage developers
+# Copyright (C) 2017-2024  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from abc import ABCMeta, abstractmethod
+import contextlib
 import datetime
 import hashlib
 import json
-from typing import Any, Dict, Optional, Sequence, Tuple, Type, Union
+from typing import Any, Dict, Iterator, Optional, Sequence, Tuple, Type, Union
 import uuid
 from xml.etree import ElementTree
 
@@ -238,18 +239,31 @@ class APIBase(APIConfig, APIView, metaclass=ABCMeta):
             swhid=meta.get("HTTP_X_CHECK_SWHID"),
         )
 
-    def _deposit_put(self, deposit: Deposit, in_progress: bool = False) -> None:
+    @contextlib.contextmanager
+    def _deposit_put(
+        self, deposit: Deposit, in_progress: bool = False
+    ) -> Iterator[None]:
         """Save/Update a deposit in db.
 
+        Acts as a context manager, ensuring the deposit object exists before entering
+        the block, and completes the deposit after (successfully) exiting the block.
+
         Args:
             deposit: deposit being updated/created
             in_progress: deposit status
         """
-        if in_progress is False:
-            self._complete_deposit(deposit)
-        else:
+        if in_progress:
             deposit.status = DEPOSIT_STATUS_PARTIAL
             deposit.save()
+            yield
+        else:
+            if deposit.pk is None:
+                # We need to save the Deposit to the database so DepositRequest objects
+                # can be created with the Deposit as foreign key
+                deposit.status = DEPOSIT_STATUS_PARTIAL
+                deposit.save()
+            yield
+            self._complete_deposit(deposit)
 
     def _complete_deposit(self, deposit: Deposit) -> None:
         """Marks the deposit as 'deposited', then schedule a check task if configured
@@ -479,16 +493,16 @@ class APIBase(APIConfig, APIView, metaclass=ABCMeta):
 
         # actual storage of data
         archive_metadata = filehandler
-        self._deposit_put(
+        with self._deposit_put(
             deposit=deposit,
             in_progress=headers.in_progress,
-        )
-        self._deposit_request_put(
-            deposit,
-            {ARCHIVE_KEY: archive_metadata},
-            replace_metadata=replace_metadata,
-            replace_archives=replace_archives,
-        )
+        ):
+            self._deposit_request_put(
+                deposit,
+                {ARCHIVE_KEY: archive_metadata},
+                replace_metadata=replace_metadata,
+                replace_archives=replace_archives,
+            )
 
         return Receipt(
             deposit_id=deposit.id,
@@ -618,17 +632,17 @@ class APIBase(APIConfig, APIView, metaclass=ABCMeta):
         self._set_deposit_origin_from_metadata(deposit, metadata_tree, headers)
 
         # actual storage of data
-        self._deposit_put(
+        with self._deposit_put(
             deposit=deposit,
             in_progress=headers.in_progress,
-        )
-        deposit_request_data = {
-            ARCHIVE_KEY: filehandler,
-            RAW_METADATA_KEY: raw_metadata,
-        }
-        self._deposit_request_put(
-            deposit, deposit_request_data, replace_metadata, replace_archives
-        )
+        ):
+            deposit_request_data = {
+                ARCHIVE_KEY: filehandler,
+                RAW_METADATA_KEY: raw_metadata,
+            }
+            self._deposit_request_put(
+                deposit, deposit_request_data, replace_metadata, replace_archives
+            )
 
         return Receipt(
             deposit_id=deposit.id,
@@ -897,17 +911,16 @@ class APIBase(APIConfig, APIView, metaclass=ABCMeta):
                 archive=None,
             )
 
-        self._deposit_put(
+        with self._deposit_put(
             deposit=deposit,
             in_progress=headers.in_progress,
-        )
-
-        self._deposit_request_put(
-            deposit,
-            {RAW_METADATA_KEY: raw_metadata},
-            replace_metadata,
-            replace_archives,
-        )
+        ):
+            self._deposit_request_put(
+                deposit,
+                {RAW_METADATA_KEY: raw_metadata},
+                replace_metadata,
+                replace_archives,
+            )
 
         return Receipt(
             deposit_id=deposit.id,