Add mention about OmniAuth.config.full_host to the documentation for rails

Hi @petro,

Welcome to the Auth0 Community!

Thanks for the contribution! Helping users break through roadblocks is what we do here, and first hand experience is a valuable resource for making that happen. Your input is highly appreciated!

I’m going to pass this along to Auth0: Secure access for everyone. But not just anyone. with your information in case there are any questions.

Thanks :smile: ,
Dan