[tooling] pin both dev and prod to same postgres version (12)

Changes

• this pins postres containers on both dev and prod to v12 (to avoid breeaking file system inconsistencies when inadvertently updatiing from one version to another via docker-compose pull or if building new system from scratch based on old data)
• it also modifies docker-compose config to enagle trust auth method on all dbs (which is necessary in postgres v12, but was no on v11)

if you were using v11 and need a workaround, there are 2 options:

• (1) if you don't mind losing data: destroy your old db and build a new one
• (2) if you want to preserve data: run a psql dump from the old version and restore it to the new one

Destructive Workaround:

cd path/to/signalboost
make dev.down
docker volume rm signalboost_postgres_data
docker-compose -f docker-compose-dev.yml pull db
make _.setup
make dev.up

Non-Destructive Workaround:

cd path/to/signalboost
make dev.down

manually edit docker-compose: change postgres:12 to postgres:11

make dev.up
docker-compose -f docker-compose-dev.yml exec -T db pg_dump -U postgres signalboost_development > db_backup
make dev.down
docker volume rm signalboost_postgres_data

manually edit docker-compose: change postgres:11 to postgres:12

docker-compose -f docker-compose-dev.yml pull db
make _.setup
make dev.up
docker-compose -f docker-compose-dev.yml exec -T db psql -U postgres -d signalboost_development < db_backup