Branch lti1.3 has a working example of a webapp which is LTI 1.3 provider
create and deploy docker image with
docker build -t devel.elearnlab.org:4567/elearn/springbootltiprovider/lti-13-provider-test-webapp .
docker push devel.elearnlab.org:4567/elearn/springbootltiprovider/lti-13-provider-test-webapp