feat(doi): add DOI-based path access for commands

Support accessing repositories using DOI strings with optional subpaths
across ls, download, metadata, and file-metadata commands.

- Implement GET v3/doi/{id}/ API model and client calls
- Parse and resolve DOI paths into respective folder and files
- Extract common folder and file resolution logic to shared helpers
- Update README with example DOI-based shell commands

mdrsclient/commands/file_metadata.py

@@ -25,13 +25,9 @@ class FileMetadataCommand(BaseCommand):
 
     @classmethod
     def file_metadata(cls, remote_path: str, password: str | None) -> None:
-        (remote, laboratory_name, r_path) = cls._parse_remote_host_with_path(remote_path)
-        r_path = r_path.rstrip("/")
-        r_dirname = os.path.dirname(r_path)
-        r_basename = os.path.basename(r_path)
+        remote = remote_path.split(":", 1)[0] if ":" in remote_path else ""
         connection = cls._create_connection(remote)
-        laboratory = cls._find_laboratory(connection, laboratory_name)
-        folder = cls._find_folder(connection, laboratory, r_dirname, password)
+        folder, laboratory, r_basename = cls._resolve_file(connection, remote_path, password)
         files = cls._find_files(connection, folder.id)
         file = find_file(files, r_basename)
         if file is None: