keycloak improvements

[depahelix2021]

keycloak is super super slow on Apple Silicon, to the point where it gums up the whole startup process for Chorus. Setting the right platform and building the keycloak image does the trick. This is the recommended method anyway, so let's do it all the time, but make sure we pass in the correct platform string to docker-compose.yml via environment variables, then set an arg for docker build for the admin password too, and then pass that down through the use of ARG and ENV in the Dockerfile. This way the admin password for keycloak can be changed at the top level without much fuss.

[epugh]

@depahelix2021 @risdenk would love another set of eyes... i think i threaded the needle of simplicity, http access to keycloak, and FAST startup wiht our preconfigured realms.

[depahelix2021]

Looks good, ship it!