Invalid `redirect_uri` in integration test

[boesing]

Bug Report

Q	A
Version(s)	latest

Summary

I experienced failing tests in #34, these are related to the league/oauth2-server v8.3.0+.

Current behavior

Tests are failing as they're using just an absolute path (/redirect) as redirect_uri which raises errors in downstream package.

thephpleague/oauth2-server#1239

How to reproduce

Just execute tests while having redirect_uri set as /redirect.

Expected behavior

Tests do not raise notice error in downstream package.

[boesing]

As pointed out in thephpleague/oauth2-server#1239, a FQDN should be passed to the downstream component.
So I assume we need to merge the redirect_uri with the base URL in case it is specified as path-only.