I have been experimenting with creating custom mix tasks and publishing them as archives.
The project is here: https://github.com/chriseyre2000/gen_docker_db/
The first release is here: https://github.com/chriseyre2000/gen_docker_db/releases/tag/0.1.0
If you download the archive and use mix archive.install gen_docker_db-0.1.0.ez
This adds a new command to mix: gen_docker_db
This will echo the command you need to create a docker container for postgres,
It is entirely insecure and uses a default password, but it will allow you to quickly stand up a local docker image for phoenix.
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