You should not need to use the docker-support interface at all. The docker interface will provide access to the Docker daemon socket to allow you to start and stop containers. You will need to either use the docker-executables content interface from the Docker snap or ship the relevant utilities or libraries you need to interact with Docker. An example of using the docker-executables interface is below (though I haven’t tested the correctness of it you should get a good idea of how it works):
plugs:
docker-executables:
interface: content
target: $SNAP/docker-exes
default-provider: docker:docker-executables
apps:
my-app:
command: ...
plugs:
- docker
- docker-executables