fix: report a locked folder as FolderLockedException

Fetching a locked folder before its password is sent returns 200 with
only its listing fields, without metadata, sub_folders and path, so
FoldersApi.retrieve failed with a pydantic ValidationError. The DOI
route fetches the folder before it can see the lock, so a
password-protected DOI folder could not be opened even with its
password.

- Add FolderLockedException, a subclass of UnauthorizedException, and
  raise it from retrieve on that short record and from the lock checks.
- On a DOI folder, send the password and fetch it again when the first
  fetch finds it locked.

mdrsclient/services.py

@@ -8,9 +8,9 @@ from mdrsclient.cache import CacheInterface
 from mdrsclient.config import ConfigFile, ConfigInterface
 from mdrsclient.connection import MDRSConnection
 from mdrsclient.exceptions import (
+    FolderLockedException,
     IllegalArgumentException,
     MissingConfigurationException,
-    UnauthorizedException,
     UnexpectedException,
 )
 from mdrsclient.models import File, Folder, Laboratory, Token, User
@@ -103,7 +103,7 @@ class MdrsService:
             raise UnexpectedException(f"Folder `{path}` not found.")
         if folders[0].lock:
             if password is None:
-                raise UnauthorizedException(f"Folder `{path}` is locked.")
+                raise FolderLockedException(f"Folder `{path}` is locked.")
             folder_api.auth(folders[0].id, password)
         return folder_api.retrieve(folders[0].id)
 
@@ -207,12 +207,20 @@ class MdrsService:
             )
 
         folder_api = FoldersApi(self.connection)
-        folder = folder_api.retrieve(doi_resp.folder_id)
+        # The folder is found by its id, so whether it is locked is known only from what
+        # retrieve returns: a full record, or the short one of a locked folder.
+        folder: Folder | None
+        try:
+            folder = folder_api.retrieve(doi_resp.folder_id)
+        except FolderLockedException:
+            folder = None
 
-        if folder.lock:
+        if folder is None or folder.lock:
             if password is None:
-                raise UnauthorizedException(f"Folder for DOI `{doi_clean}` is locked.")
+                raise FolderLockedException(f"Folder for DOI `{doi_clean}` is locked.")
             folder_api.auth(doi_resp.folder_id, password)
+            if folder is None:
+                folder = folder_api.retrieve(doi_resp.folder_id)
 
         lab_api = LaboratoriesApi(self.connection)
         labs = lab_api.list()