Change effective on 01 March 2017
Previously when a Rails app was deployed a Postgres database would be provisioned via an add-on through
bin/release. After this change, the application being deployed must include a Postgres driver gem in the
Gemfile to get a free Heroku Postgres add-on provisioned. This is the list of Gems that are detected for provisioning the Postgres add-on.
This change does not affect manual provisioning of the Heroku Postgres add-on. This is documented in the Ruby Support Documentation.