[proposal] docker-compose - backend selection on startup

[desmax74]

Is your feature request related to a problem? Please describe.

Currently the backend used with docker compose is in memory and is started with docker compose up, to switch from inmem to ent/neo4j/arangodb is needed to add or uncomment the desidered backend in the services section of the docker-compose.yaml and must be changed manually the guac.yaml the backend in the value of gql-backend: https://github.com/guacsec/guac/blob/main/container_files/guac/guac.yaml#L20

Describe the solution you'd like

Splitting the configurations using a file with services per backend and a guac.yaml per backend (currently guac.yaml contains the configuration for all backends) we can choose the backend on startup without manual changes and with a cmd like this

docker compose -f docker-compose.yml -f container_files/<backend>.yaml up

each .yaml point to its specific guac.yaml configuration with
volumes: - ./container_files/guac_<backend>:/guac:z