Docs: Add documentation (or command) for running test SAML server

[kadamwhite]

When developing this plugin, we need to be able to run a SAML provider to validate and test the WordPress plugin properly integrates with the authentication provider.

This shell command has been provided by the Altis team as a way to spin up a local identify provider:

    docker run --name=localsaml \
        -p 8086:8080 \
        -p 8443:8443 \
        -e SIMPLESAMLPHP_SP_ENTITY_ID=https://<your-local-wordpress-url>/ \
        -e SIMPLESAMLPHP_SP_ASSERTION_CONSUMER_SERVICE=https://<your-local-wordpress-url>/sso/verify \
        -e SIMPLESAMLPHP_SP_SINGLE_LOGOUT_SERVICE=https://<your-local-wordpress-url>/sso/logout \
        -d --rm kristophjunge/test-saml-idp

Warning

This docker container is not build for Apple Silicon. If using Docker Desktop, you need to be using the Apple Virtualization Framework and need Rosetta enabled.

Notes

• The trailing slash on the entity ID is required

[goldenapples]

This documentation currently exists in the Wiki: https://github.com/humanmade/wp-simple-saml/wiki/Testing-SSO-locally

#103 updates the "Testing Locally" page as part of moving the documentation into docsify. However, we want to update the plugin documentation to use just-the-hm-docs instead, so that PR is still open.

#103 (comment)