New postgres image version is available on docker registry with tag 12-debezium - https://hub.docker.com/r/openlmis/postgres/tags
Upgrade instructions for each version can be found on postgres page https://www.postgresql.org/docs/current/upgrading.html
In order to properly upgrade database additional steps might be required, depending on the deployed instance:
postgis extension upgrade (compatbility matrix: https://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS )
generic upgrade instructions are here https://postgis.net/workshops/postgis-intro/upgrades.html
aws rds specific https://aws.amazon.com/blogs/database/best-practices-for-upgrading-amazon-rds-to-major-and-minor-versions-of-postgresql/
review of custom jasper reports (might contain custom sql which is not compatible)
review of CI/CD tools as they might use docker version incompatible with new openlmis postgres image
It is recommended to make full backup before any upgrade to prevent data loss.