Update the kosmos-mastodon cookbook to use the new postgresql cookbook

Don't depend on the deprecated database cookbook to create the database

site-cookbooks/kosmos-mastodon/templates/default/env.production.erb

@@ -1,9 +1,15 @@
 # Service dependencies
 REDIS_URL=<%= @redis_url %>
 DB_HOST=localhost
-DB_USER=postgres
 DB_NAME=mastodon
+# Remove the condition once we have migrated mastodon to andromeda
+<% if node[:platform_version].to_f < 18.04 -%>
+DB_USER=postgres
 DB_PASS=<%= node['postgresql']['password']['postgres'] %>
+<% else -%>
+DB_USER=mastodon
+DB_PASS=<%= @db_pass %>
+<% end -%>
 DB_PORT=5432
 
 # Federation