Add MIME Type Detection and OAuth2 Token Refresh with Updated Authorization Flow

[vsychov]

This pull request introduces two key improvements and an essential update to the project:

1. Automatic MIME Type Detection:

   • Implemented logic to automatically determine the MIME type of files based on their extensions.
   • Ensures that file previews in Google Drive work correctly by associating the appropriate MIME type.

2. OAuth2 Token Refresh:

   • Added functionality to refresh OAuth2 tokens automatically.
   • Ensures continuous authentication without requiring manual intervention by persisting updated tokens to a file.

3. Updated OAuth Redirect URL:

   • Replaced the deprecated urn:ietf:wg:oauth:2.0:oob flow with a "fake" https://localhost redirect URL.
   • This update complies with Google’s deprecation of the OOB flow and allows developers to copy the authorization code for successful authentication.

Key Benefits:

• Enhanced user experience with accurate MIME type detection for file previews.
• Improved reliability and usability of OAuth2 authentication with token refresh and updated redirect URL.
• Compatibility with Google’s latest OAuth2 standards.

Please review the changes and provide feedback. Thank you!

Fix #214