Add points how to prepare for database reviews
Add points how to prepare for database reviews

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/65126.

Came up in the database office hours call on 2019-07-25.

stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq