Migrating from libsignon-glib 1.x to libsignon-glib 2.x: libsignon-glib Reference Manual

## Migrating from libsignon-glib 1.x to libsignon-glib 2.x

The whole API has been reworked to be easily usable with the GObject Introspection. It now fully uses the GTask API internally and provides the expected asynchronous functions instead of relying on callbacks.

This helps to keep the objects lifecycle sane across the projects. But it required some invasive changes in the API.

## Changes in SignonAuthService

`signon_auth_service_query_mechanisms()` has been changed into `signon_auth_service_get_mechanisms()`. There is no more custom callback to use, only the GAsyncResult API. Use `signon_auth_service_get_mechanisms_finish()` in your GAsyncReadyCallback to get the mechanisms.

In a same manner `signon_auth_service_query_methods()` has been changed to `signon_auth_service_get_methods()`.

There are now synchronous methods to get the methods and mechanisms.