✨ feat(server): Add user login endpoint

Added a new endpoint for user login in the server.py file. The login
endpoint allows users to log in and returns the result. If any error
occurs during the login process, an exception is logged and a 500
status code is returned.

The new endpoint is defined as a POST request at `/user/login`. The
request body expects a `Login` object.

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "novelai-python"
-version = "0.1.9"
+version = "0.2.0"
 description = "Novelai Python Binding With Pydantic"
 authors = [
     { name = "sudoskys", email = "[email protected]" },