The API shall be simple, yet powerful. Introspection seemed like cool idea, but
is not required.

There are limited amount of endpoints. There are few parameters. Those things
shall be documented.

Backward compatibility is easy. Adding new endpoint or parameter shall be always
optional.

In case of rewriting versioning will be used.

After activating Vifib Facebook Server Extraction Plugin it is possible to use
facebook authorisation in Vifib.

Persons will be automatically created thanks to reusing REST API call, which has
already logic for Facebook user initial synchronisation.

Reuse 202 code, same like with request, to inform, that user has been allowed
to access, but not created yet.

Split internal and external ones.
Explain how to use Facebook authentication.