🚑️(backend) command to update attachment content-type

The uploaded files in the system are missing
the content-type.
We add a command to update the content-type of
the existing uploaded files.
This command will run one time when we will deploy
to the environments.

src/backend/core/tests/commands/test_update_files_content_type_metadata.py

@@ -0,0 +1,50 @@
+"""
+Unit test for `update_files_content_type_metadata` command.
+"""
+
+import uuid
+
+from django.core.files.storage import default_storage
+from django.core.management import call_command
+
+import pytest
+
+from core import factories
+
+
+@pytest.mark.django_db
+def test_update_files_content_type_metadata():
+    """
+    Test that the command `update_files_content_type_metadata`
+    fixes the ContentType of attachment in the storage.
+    """
+    s3_client = default_storage.connection.meta.client
+    bucket_name = default_storage.bucket_name
+
+    # Create files with a wrong ContentType
+    keys = []
+    for _ in range(10):
+        doc_id = uuid.uuid4()
+        factories.DocumentFactory(id=doc_id)
+        key = f"{doc_id}/attachments/testfile.png"
+        keys.append(key)
+        fake_png = b"\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR..."
+        s3_client.put_object(
+            Bucket=bucket_name,
+            Key=key,
+            Body=fake_png,
+            ContentType="text/plain",
+            Metadata={"owner": "None"},
+        )
+
+    # Call the command that fixes the ContentType
+    call_command("update_files_content_type_metadata")
+
+    for key in keys:
+        head_resp = s3_client.head_object(Bucket=bucket_name, Key=key)
+        assert (
+            head_resp["ContentType"] == "image/png"
+        ), f"ContentType not fixed, got {head_resp['ContentType']!r}"
+
+        # Check that original metadata was preserved
+        assert head_resp["Metadata"].get("owner") == "None"