Create postgres user to avoid fatal warning

docker/init-invidious-db.sh

@@ -1,6 +1,10 @@
 #!/bin/sh
 set -eou pipefail
 
+psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+  CREATE USER postgres;
+EOSQL
+
 psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/channels.sql
 psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/videos.sql
 psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/channel_videos.sql