Increase DB connection pool size for specs

A spec failed with this message:

  ActiveRecord::ConnectionTimeoutError:
    could not obtain a connection from the pool within 5.000 seconds (waited 5.000 seconds); all pooled connections were in use

The error seems to be raised when trying to authenticate the user
through Devise in a before_action block. Increasing the pool size by one
helped.

I don't know why our app needs more than 5 connections at the same time.
Maybe some gem "forgets" to release connections?

config/database.yml

@@ -1,7 +1,7 @@
 defaults: &defaults
   adapter: postgresql
   encoding: unicode
-  pool: <%= ENV.fetch('OFN_DB_POOL', 5) %>
+  pool: <%= ENV.fetch('OFN_DB_POOL', 6) %>
   host: <%= ENV.fetch('OFN_DB_HOST', 'localhost') %>
   username: <%= ENV.fetch('OFN_DB_USERNAME', 'ofn') %>
   password: <%= ENV.fetch('OFN_DB_PASSWORD', 'f00d') %>