To make Micropub requests, the specification requires a Bearer token. Many current Micropub clients force the user to go through IndieAuth to obtain this, which means you need to have the required authorization and token endpoints set-up before getting started with Micropub.
The file token-provider.php
implements the happy path for the IndieAuth dance resulting in providing the Micropub client with whatever token the user has provided.
raziellight on IRC was trying to get the Micropub client Omnibear to work, and that required him to figure out how to set-up IndieAuth from scratch. I think this is way too big of an investment for getting started with Micropub. It was time to cut out the middle man (or protocol, in this case