Increased continuation size and change auth

Created by: oblivisheee

This pull request includes significant changes to the assistant/src/interfaces.rs file to improve token handling and authentication, as well as updates to the conf/nginx.conf file to handle CORS preflight requests. The most important changes are summarized below:

Improvements to Token Handling and Authentication:

• assistant/src/interfaces.rs: Updated the chat_session function to use query parameters for tokens instead of headers. This includes modifications to extract auth_token and session_token from the query parameters. [1] [2]
• assistant/src/interfaces.rs: Introduced a new helper function token_string_from_header to convert token headers to strings, and updated various functions (get_chat, get_chats, create_chat, delete_chat) to use this helper function. [1] [2] [3] [4]
• assistant/src/interfaces.rs: Refactored auth_token_with_nats to directly accept a string token instead of a header, improving the clarity and efficiency of token verification. [1] [2]
• assistant/src/interfaces.rs: Modified process_session_token to accept an optional string token instead of a header, streamlining session token processing.

CORS Preflight Request Handling:

• conf/nginx.conf: Added handling for CORS preflight requests by returning a 204 status for OPTIONS requests across various locations, ensuring proper CORS headers are set. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]Auth now is implemented via query params