Create medium psql redudant DB in stage

[patphongs]

Summary

What we're after:
In order to closely mirror and test our Wagtail database in production, we need to create a new medium psql redundant DB in our staging environment.

Completion criteria

• Medium redundant psql Wagtail database is used in stage

Tech steps or considerations

• Create the medium redundant psql database service in stage
• Bind this new service to the cms app
• Unbind the old service from the cms app
• Check if this is a dedicated instance like in production
• Check max connection pool settings are the same as production

[patphongs]

This has been created in stage. All the configs are the same as prod.