Create a separate PostgreSQL node so we can support multiple Discourse Docker instances

[renoirb]

Discourse supports only PostgreSQL, let’s create an instance to persist conversations if we need to deploy more than one Discourse containers.

Since we have nothing else that use PostgreSQL and that Discourse already has backup mechanism, we WON’T have backups from there. We’ll use instead Discourse’s ref: webplatform/ops#154

Tasks

• [x] Create PostgreSQL server VM role
• [x] Ensure VM type has no conflicts with other database related states

  Related

• webplatform/ops#154 Backups in Discourse

[renoirb]

Sent in "Work status update" email on devrel list

[renoirb]

One thing left to do; I see a few errors in the logs due to conflict in database related states. Fix before closing.