Support Chart Defined RabbitMQ User and Virtual Host Creation

This blueprint proposes normalizing the handling of rabbitmq with mariadb, where users, databases, and permissions are created per the specification in the calling service chart.

This would leverage an admin section in the rabbitmq endpoint to orchestrate the creation of chart/service specific rabbitmq users (as defined in the user section of the rabbitmq endpoint) as well as create virtual hosts should they not exist, and grant appropriate permissions to the newly created user.

All of this should be cognizant of the fact that it is possible that the non-admin same user could be used by multiple services and avoid undoing permission grants potentially granted by another service for the same user.