Feature request - add env var to enable extensions by default

[yhojann-cl]

By example, when need enable by default the uuid extension need execute additional scripts in startup:

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

But, is a great idea send the extensions by arguments, by example:

$ sudo docker run postgres -e "EXTENSION=uuid-ossp" -e "EXTENSION=other-extension" ...

[yosifkit]

Basically the same response as, docker-library/mongo#460 (comment); tldr: "We are always very hesitant to add new environment variables."

And I'll add, especially for something that amounts to a two line dockerfile (or an extra line in a docker-compose.yml file to mount an initdb.d directory):

FROM postgres:13
RUN echo 'CREATE EXTENSION IF NOT EXISTS "uuid-ossp";' > /docker-entrypoint-initdb.d/uuid-ossp.sql

[yhojann-cl]

But can not use docker compose, why not use enviroment variable for easy enabling extension?, is same question: why pass the password on enviroment variable and not in docker compose using RUN and create user statement?, in a productive enviroment need enable very specific extensions and dynamics passwords.