POC for rest issues in keycloak extensions for keycloak 23.0.5

Steps to reproduce

• navigate to ./rest and run mvn clean verify; docker build -t keycloakpoc2305 .; docker run -p 8080:8080 keycloakpoc2305
• wait until keycloak has fully started and has initialized extensions

containerresponse/requestfilters:

run the FilterTests in the org.sostrich.keycloak.pocs package

multipart

run the MultipartTests in the org.sostrich.keycloak.pocs package