The one small part of it I worked with (registering users) was very easy. Documentation was clear with example code in a stack of popular backend languages. Ou

The one small part of it I worked with (registering users) was very easy. Documentation was clear with example code in a stack of popular backend languages. Our backend is all PHP, so I just pulled in their Composer package. As I recall, all I had to do was pass it customer information and a redirect URL for where to send users after completion, and it handled the rest.