Add in_review_folder to usage ping

As its hard to reliably check how many review apps there are on the
clients machine, we start by checking where the type is `review`. This
means the folder is called that way. This will lead to a seq
scan on the table. However, this is done once a week, so the benefit of
adding an index seems not to apply here.

app/models/environment.rb

@@ -45,6 +45,7 @@ class Environment < ActiveRecord::Base
       to_sql
     order(Gitlab::Database.nulls_first_order("(#{max_deployment_id_sql})", 'ASC'))
   end
+  scope :in_review_folder, -> { where(environment_type: "review") }
 
   state_machine :state, initial: :available do
     event :start do

changelogs/unreleased/zj-review-apps-usage-data.yml

+---
+title: Add review apps to usage metrics
+merge_request: 12185
+author:

lib/gitlab/usage_data.rb

@@ -27,6 +27,7 @@ module Gitlab
             deploy_keys: DeployKey.count,
             deployments: Deployment.count,
             environments: Environment.count,
+            in_review_folder: Environment.in_review_folder.count,
             groups: Group.count,
             issues: Issue.count,
             keys: Key.count,

spec/lib/gitlab/usage_data_spec.rb

@@ -37,6 +37,7 @@ describe Gitlab::UsageData do
         deploy_keys
         deployments
         environments
+        in_review_folder
         groups
         issues
         keys