STYLE: Linting python files and making it fully typed (#298)

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[AB#36303](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/36303)
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[AB#38478](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/38478)

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> GitHub Issue: #22

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### Summary   
This pull request refactors the `mssql_python` package to improve type
safety and code clarity by adding explicit type annotations throughout
the codebase. The changes mainly focus on the `__init__.py` and
`auth.py` modules, updating function signatures, global variables, and
constants to use Python type hints. This will help with static analysis,
improve IDE support, and make the code easier to understand and
maintain.

### Type Annotation Improvements

* Added type annotations to global variables, constants, and function
signatures in `mssql_python/__init__.py`, including SQL constants and
configuration settings.
* Updated function signatures in `mssql_python/auth.py` to use type
hints for parameters and return types, such as changing raw
`list`/`dict` usage to `List[str]`, `Dict[int, bytes]`, and
`Optional[...]`.

### Code Quality and Consistency

* Improved formatting for multi-line statements and error messages, and
standardized quote usage for strings.
* Updated class and method definitions to use explicit type annotations
for attributes and properties, especially in the `Settings` and custom
module classes.

### Minor Logic and Readability Enhancements

* Improved parameter exclusion logic and connection string validation
for authentication handling in `auth.py`.
* Ensured that sensitive parameters are more robustly excluded from
connection strings.

These changes collectively enhance the maintainability and robustness of
the codebase by leveraging Python's type system and improving code
readability.

Author: jahnvi480

mssql_python/__init__.py

@@ -6,12 +6,13 @@
 
 import platform
 import struct
-from typing import Tuple, Dict, Optional, Union
+from typing import Tuple, Dict, Optional, List
 from mssql_python.constants import AuthType
 
+
 class AADAuth:
     """Handles Azure Active Directory authentication"""
-    
+
     @staticmethod
     def get_token_struct(token: str) -> bytes:
         """Convert token to SQL Server compatible format"""
@@ -21,22 +22,30 @@ def get_token_struct(token: str) -> bytes:
     @staticmethod
     def get_token(auth_type: str) -> bytes:
         """Get token using the specified authentication type"""
-        from azure.identity import (
-            DefaultAzureCredential, 
-            DeviceCodeCredential, 
-            InteractiveBrowserCredential
-        )
-        from azure.core.exceptions import ClientAuthenticationError
-        
+        # Import Azure libraries inside method to support test mocking
+        # pylint: disable=import-outside-toplevel
+        try:
+            from azure.identity import (
+                DefaultAzureCredential,
+                DeviceCodeCredential,
+                InteractiveBrowserCredential,
+            )
+            from azure.core.exceptions import ClientAuthenticationError
+        except ImportError as e:
+            raise RuntimeError(
+                "Azure authentication libraries are not installed. "
+                "Please install with: pip install azure-identity azure-core"
+            ) from e
+
         # Mapping of auth types to credential classes
         credential_map = {
             "default": DefaultAzureCredential,
             "devicecode": DeviceCodeCredential,
             "interactive": InteractiveBrowserCredential,
         }
-        
+
         credential_class = credential_map[auth_type]
-        
+
         try:
             credential = credential_class()
             token = credential.get_token("https://database.windows.net/.default").token
@@ -50,18 +59,21 @@ def get_token(auth_type: str) -> bytes:
             ) from e
         except Exception as e:
             # Catch any other unexpected exceptions
-            raise RuntimeError(f"Failed to create {credential_class.__name__}: {e}") from e
+            raise RuntimeError(
+                f"Failed to create {credential_class.__name__}: {e}"
+            ) from e
+
 
-def process_auth_parameters(parameters: list) -> Tuple[list, Optional[str]]:
+def process_auth_parameters(parameters: List[str]) -> Tuple[List[str], Optional[str]]:
     """
     Process connection parameters and extract authentication type.
-    
+
     Args:
         parameters: List of connection string parameters
-        
+
     Returns:
         Tuple[list, Optional[str]]: Modified parameters and authentication type
-        
+
     Raises:
         ValueError: If an invalid authentication type is provided
     """
@@ -88,7 +100,7 @@ def process_auth_parameters(parameters: list) -> Tuple[list, Optional[str]]:
                 # Interactive authentication (browser-based); only append parameter for non-Windows
                 if platform.system().lower() == "windows":
                     auth_type = None  # Let Windows handle AADInteractive natively
-                
+
             elif value_lower == AuthType.DEVICE_CODE.value:
                 # Device code authentication (for devices without browser)
                 auth_type = "devicecode"
@@ -99,40 +111,50 @@ def process_auth_parameters(parameters: list) -> Tuple[list, Optional[str]]:
 
     return modified_parameters, auth_type
 
-def remove_sensitive_params(parameters: list) -> list:
+
+def remove_sensitive_params(parameters: List[str]) -> List[str]:
     """Remove sensitive parameters from connection string"""
     exclude_keys = [
-        "uid=", "pwd=", "encrypt=", "trustservercertificate=", "authentication="
+        "uid=",
+        "pwd=",
+        "encrypt=",
+        "trustservercertificate=",
+        "authentication=",
     ]
     return [
-        param for param in parameters
+        param
+        for param in parameters
         if not any(param.lower().startswith(exclude) for exclude in exclude_keys)
     ]
 
+
 def get_auth_token(auth_type: str) -> Optional[bytes]:
     """Get authentication token based on auth type"""
     if not auth_type:
         return None
-        
+
     # Handle platform-specific logic for interactive auth
     if auth_type == "interactive" and platform.system().lower() == "windows":
         return None  # Let Windows handle AADInteractive natively
-        
+
     try:
         return AADAuth.get_token(auth_type)
     except (ValueError, RuntimeError):
         return None
 
-def process_connection_string(connection_string: str) -> Tuple[str, Optional[Dict]]:
+
+def process_connection_string(
+    connection_string: str,
+) -> Tuple[str, Optional[Dict[int, bytes]]]:
     """
     Process connection string and handle authentication.
-    
+
     Args:
         connection_string: The connection string to process
-        
+
     Returns:
         Tuple[str, Optional[Dict]]: Processed connection string and attrs_before dict if needed
-        
+
     Raises:
         ValueError: If the connection string is invalid or empty
     """
@@ -145,9 +167,9 @@ def process_connection_string(connection_string: str) -> Tuple[str, Optional[Dic
         raise ValueError("Connection string cannot be empty")
 
     parameters = connection_string.split(";")
-    
+
     # Validate that there's at least one valid parameter
-    if not any('=' in param for param in parameters):
+    if not any("=" in param for param in parameters):
         raise ValueError("Invalid connection string format")
 
     modified_parameters, auth_type = process_auth_parameters(parameters)
@@ -158,4 +180,4 @@ def process_connection_string(connection_string: str) -> Tuple[str, Optional[Dic
         if token_struct:
             return ";".join(modified_parameters) + ";", {1256: token_struct}
 
-    return ";".join(modified_parameters) + ";", None
+    return ";".join(modified_parameters) + ";", None