Feature request: allow additional database options

[dale-wahl]

It ought to be possible to allow further configuration of database connections (a PR was proposed but needed additional work #285). Instead of individual parameters being stored in the .env file and config.ini file, psql allows strings to be passed.

E.g. psql --host=$POSTGRES_HOST --port=$POSTGRES_PORT --user=$POSTGRES_USER --dbname=$POSTGRES_DB becomes psql "host=$POSTGRES_HOST port=$POSTGRES_PORT user=$POSTGRES_USER password=$POSTGRES_PASSWORD dbname=$POSTGRES_DB".

To make that change, it would have to work with both psql in files like docker/docker-entrypoint.sh as well as with our Database class. And the string would need to be passed via docker/docker_setup.py to the [https://github.com/digitalmethodsinitiative/4cat/blob/master/common/config_manager.py](config manager).

Opening this issue to track any need/interest of such a feature.