Modify healthcheck to check database readiness (#363)

Updated healthcheck command to include database name.

Author: krokosik

docker/prod/compose.yml

@@ -11,7 +11,7 @@ services:
       - POSTGRES_DB=${POSTGRES_DB:?err}
       - POSTGRES_PORT=${POSTGRES_PORT:-5432}
     healthcheck:
-      test: ['CMD-SHELL', 'pg_isready -U ${POSTGRES_USER}']
+      test: ['CMD-SHELL', 'pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}']
       interval: 10s
       timeout: 5s
       retries: 5