Is your feature request related to a problem? Please describe.
When querying APIs that require Basic Authentication, there's no straightforward way to pass credentials. Currently, I have to manually encode credentials to base64 and construct the Authorization header myself, which is cumbersome compared to tools like curl that handle this automatically with the --user username:password flag.

Describe the solution you'd like
Add a user_credentials column to the net_http_request table that accepts credentials in the format username:password. The plugin should automatically encode these credentials and add the appropriate Authorization: Basic header to the request, similar to curl's --user flag.

Example:

SELECT 
  response_body, response_status_code 
FROM 
  net_http_request 
WHERE 
  url = 'https://api.example.com/data' 
  AND user_credentials = 'myuser:mypassword'
  AND insecure = true;

Describe alternatives you've considered

• Manually encoding credentials to base64 and passing via request_headers = '{"Authorization": "Basic base64string"}' - this works but requires extra steps and is error-prone
• Creating a separate connection configuration for auth - would be overkill for simple Basic Auth
• Using environment variables - less flexible in Pipes or other locations
• I tried the example in the docs for using in request_body but was not passing correctly and was clunky with json.