Add method to the database connection class indicating the use of relational database storage

Problem/Motivation

In ✨ [meta] Add database driver for MongoDB to Core as experimental Active we are adding a database driver for MongoDB. MongoDB does not use a relational database storage. We should add a method to the database connection class that returns TRUE when the database driver uses a relational database storage and FALSE when it does not.

Proposed resolution

Add the method Connection::usesRelationalDatabaseStorage()

Remaining tasks

Do it.

User interface changes

None

API changes

Added new method Connection::usesRelationalDatabaseStorage()

Data model changes

None

Release notes snippet

TBD