♻️(backend) merge room name regex and centralize patterns in enums

Combine the regex used in Drive with the one from the recording
feature and centralize them in the enums module.

Although the module name suggests only enums, it also hosts
shared constants used across the codebase.

src/backend/core/enums.py

@@ -17,6 +17,12 @@ RECORDING_STORAGE_URL_PATTERN = re.compile(
     f"/media/{settings.RECORDING_OUTPUT_FOLDER}/(?P<recording_id>{UUID_REGEX:s}).(?P<extension>{FILE_EXT_REGEX:s})"
 )
 
+MEDIA_STORAGE_URL_PATTERN = re.compile(
+    f"{settings.MEDIA_URL:s}"
+    rf"(?P<key>{settings.FILE_UPLOAD_PATH:s}/(?P<pk>{UUID_REGEX:s})\.{FILE_EXT_REGEX:s})$"
+)
+
+
 # Django sets `LANGUAGES` by default with all supported languages. We can use it for
 # the choice of languages which should not be limited to the few languages active in
 # the app.