Follow-up from "Geo: add documentation"

The following discussions from !1041 (merged) should be addressed:

• @twk3 started a discussion: (+6 comments)

  This step cannot be run before the first reconfigure, as the rails environment isn't created yet. We should move this somewhere after reconfigure.

• @twk3 started a discussion: (+2 comments)

  This will overwrite the pg_hba entries, so we either need to run reconfigure again after this, or you need to have all your secondary application node CIDRs added to the primary db's config.

• @twk3 started a discussion: (+2 comments)

  Many of these return something different until after you've added the Node to the primary through the UI:

  GitLab Geo secondary database is correctly configured ... not a secondary node
  Database replication enabled? ... not a secondary node
  Database replication working? ... not a secondary node
  GitLab Geo tracking database is configured to use Foreign Data Wrapper? ... not a secondary node
  GitLab Geo tracking database Foreign Data Wrapper schema is up-to-date? ... not a secondary node
  GitLab Geo HTTP(S) connectivity ... not a secondary node

  These geo checks should be done after we've added the secondary to the primary