Misleading error message for missing group-id flag when running publish.

[jamesross3]

When ./godelw conjure-publish is run without the group-id flag specified, the error message is:

Error: group-id was not specified -- it must be specified in configuration or using a flag

However, there doesn't seem to be a configuration point for actually specifying the group ID. Looks like this was left as a todo here.

I think we should either (1) fix the error message to avoid misleading people here, or (2) support specifying the group ID in the plugin configuration.