Multistage Dockerfile

[yksflip]

This PR

• removes a db dependency for assets precompilation
• adds rswag swaggerize swagger.yml generation and thatfore introduces the nulldb adapter (generate swagger.yml in dockerfile (rswag) #998)
• remove Dockerfile-dev
• unites dev and production image in one File using docker multi-stage

[yksflip]

any thoughts @paroga @wvengen ? :)

[wvengen]

Awesome!
Not sure though about merging the production and dev Dockerfile. I think the Dockerfile is complex enough without it. And does it mean by doing docker build -t foodsoft . builds both the development and production image?
Also, when building the swagger file, I would expect it to have RAILS_ENV=production, e.g. routes might be affected by the environment.

[wvengen]

p.s. in other projects, I've used a dummy DATABASE_URL without even needing the nulldb adapter - but I guess it's cleaner

[yksflip]

thanks for your comments!
Hm yeah I see what you mean. I thought it could reduce complexity and I liked the multi-stage idea, but in the end everything blew up a bit.

You can choose what target to build with e.g. docker build --target development, but the production stage requires the development as it copies the swagger.yml file.
We could generate the swagger.yml in the production stage, but that would require the rswag gem in the prod group.

Good point about the RAILS_ENV, I think I used test as the rswag-specs gem is not part of the production group. Afaic the swagger file is generated by the definitions of the spec/requests/ tests. But I can double check if it makes any differences.

What a hack with the DATABASE_URL, I didn't know. I think I'd even prefer that than having another dependency ...