Enhance OxiAPI and Node classes with type hints and property updates

- Updated the `OxiAPI` class to check for `None` explicitly when setting authentication credentials.
- Added type hints to the `Node` class and introduced a TODO for future enhancements.
- Refactored properties in the `NodeView` class to include type hints and improved handling of optional data retrieval.

oxi/interfaces/contract.py

@@ -8,7 +8,7 @@ class Base(BaseModel):
 
 class System(BaseModel):
     """
-    Requred
+    Required
     """
 
     model: str
@@ -18,7 +18,7 @@ class System(BaseModel):
 
 class Interfaces(Base):
     """
-    Requred
+    Required
     """
 
     name: str = Field(alias="interface")