Docker configuration from productDependencies can fail if the service doesnt publish its docker image

[qinfchen]

What happened?

Improvement from #239 has an implicit assumption that every sls service being declared in the product dependency must have docker images with matching group and service name.

This line will throws the following exception even if the image is not being used.

Execution failed for task ':generateDockerCompose'.
> Could not resolve all dependencies for configuration ':docker'.
   > Could not find com.test:serviceB:0.0.0.
     Required by:
         project : > project :test-server-A

Questions:

1. is it required for a sls service to publish a docker image that shares the same name?

2. should this plugin throw the above exception if the docker image is not being used in the docker compose rule?