Add full integration test

[bbockelm]

Add a full integration test, using the integration tests in github.com/PelicanPlatform/xrdcl-pelican as an inspiration.

Create a CTest-based setup and tear down fixture. The setup should create a TLS CA and host certificate, create the key and JWKS using tools in this repo, then launch a small python-based web server that hosts a JWKS and can do discovery. The Python web app should write into a build directory when it is fully started so the parent process knows when to proceed.

It should write out a setup.sh file in a build directory that contains the issuer URL (do not use fixed ports but rather dynamically bind to port 0 to get an open one) and the python process's PID.

The tests leveraging the fixture should read the setup.sh file and use that for any input or configuration needed to run the test.

The tear down should similarly read the setup.sh to kill the test server by PID.