The logic looks circular to me(although I know I'm missing something)
I want to use this:
But in order to make the url to send the user to get the pin you need an "oauth_token" :
But to get the "oauth_token" you need a:
But that at the bottom shows it needs an "oauth_signature"
Well, an "oauth_signature" requires an "oauth_token" ( https://dev.twitter.com/docs/auth/creating-signature ) which you don't have, making impossible to get an "oauth_token" because you need one to get one.
What am I missing here? I mainly just want to find out how to get that initial url for the PIN-based authorization, so I need that first "oauth_token" somehow.
There are two different types of oauth tokens - let's call them request tokens and normal tokens. Request tokens are used for the authentication, then once the authentication is done you get normal oauth tokens.
oauth/request_token will generate a request token for you, which is a temporary token used for the actual authentication. Once that's done you have the normal tokens.