🐛(backend) allow any type of extensions for media download

The regex to validate media file extensions was too restrictive.

src/backend/core/api/viewsets.py

@@ -38,7 +38,7 @@ ATTACHMENTS_FOLDER = "attachments"
 UUID_REGEX = (
     r"[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}"
 )
-FILE_EXT_REGEX = r"\.[a-zA-Z]{3,4}"
+FILE_EXT_REGEX = r"\.[a-zA-Z0-9]{1,10}"
 MEDIA_STORAGE_URL_PATTERN = re.compile(
     f"{settings.MEDIA_URL:s}(?P<pk>{UUID_REGEX:s})/"
     f"(?P<key>{ATTACHMENTS_FOLDER:s}/{UUID_REGEX:s}{FILE_EXT_REGEX:s})$"