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/cp.py

@@ -29,8 +29,8 @@ class CpCommand(BaseCommand):
 
     @classmethod
     def cp(cls, src_path: str, dest_path: str, is_recursive: bool) -> None:
-        (s_remote, s_laboratory_name, s_path) = cls._parse_remote_host_with_path(src_path)
-        (d_remote, d_laboratory_name, d_path) = cls._parse_remote_host_with_path(dest_path)
+        s_remote, s_laboratory_name, s_path = cls._parse_remote_host_with_path(src_path)
+        d_remote, d_laboratory_name, d_path = cls._parse_remote_host_with_path(dest_path)
         if s_remote != d_remote:
             raise IllegalArgumentException("Remote host mismatched.")
         if s_laboratory_name != d_laboratory_name: