this differs from the standard config in that it adds a volume to mount your custom config file:
and then adds a command to use that config file instead of the default:
command: postgres -c config_file=/etc/postgresql.conf
of course make sure you like, have a custom config file at postgres/postgresql.conf or change the first part of that volumes command to point to wherever yours is but next time you build/restart it will load that config file.
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