Add a GET route for validate tunnel so we can use caddy on_demand

[SiebeVE]

https://caddyserver.com/docs/json/apps/tls/automation/on_demand/ask/

[what-the-diff]

PR Summary

• Addition to .gitignore
  We've made improvements to protect sensitive details by adding db.db to the .gitignore file. This ensures that our database doesn't inadvertently get exposed in the public code.
• Updated Server Factory
  The app/Server/Factory.php file has been updated to handle a new route (/validate-tunnel). An additional mechanism, addValidateTunnel(), has been added to facilitate this new routing.
• New File: ValidateTunnelController
  A new file app/Server/Http/Controllers/ValidateTunnelController.php has been introduced. This forms part of our efforts to manage new requests efficiently. It specifically deals with the handling of requests to /validate-tunnel.
• Updates in configuration
  We've included a new configuration for validate_tunnel in the config/expose.php file. It accommodates an authorized key, therefore enhancing our security measures.