Hi @Ed_Bobkov
Well, there very well may be some “other method” that I do not know about 
I defer to others for that.
I worked on this for many days a while back, and this was the “best I could come up with” after a lot of different “trial and errors”.
If there is an easier way, I would love to hear about it; but it does make sense if you work with Docker a lot.
First of all, the image must be built. Discourse starts with a base image and modifies it. When you add new plugins in production (Docker), you generally need to rebuild the container. Hence, that’s why I replied as I did above.
There are a lot of people here smarter than me on the topic of Discourse system admin, so maybe someone else has a better idea along the lines of what you are looking for.
Cheers!