refactor: extract MdrsClient service layer for library portability

To improve the tool's portability as a Python library, the core logic
has been decoupled from the CLI interface. This allows developers to
programmatically interact with MDRS without relying on CLI-specific
argument parsing or local file-based caches.

- Introduce `MdrsClient` service layer to handle core operations.
- Abstract authentication state using `CacheInterface` and `InMemoryCache`.
- Migrate all CLI commands to utilize `MdrsClient` for execution.
- Separate `Doi` data model from API responses and move to `models/doi.py`.
- Update `README.md` to include Python API usage examples.
- Bump package version to 1.3.17.

mdrsclient/commands/base.py

@@ -196,7 +196,7 @@ class BaseCommand(ABC):
         folder_api = FoldersApi(connection)
 
         # Retrieve full folder detail directly by ID; laboratory_id is here.
-        folder = folder_api.retrieve(doi_resp.folder.id)
+        folder = folder_api.retrieve(doi_resp.folder_id)
 
         if folder.lock:
             if password is None: