[client-connection] add a repo property for dbapi compatibility
To ease transition from dbapi to repoapi we need the ClientConnection to be as
compatible as possible with the dbapi. Adding this method goes in this
direction.
It'll get deprecated in the deprecation wave that will conclude the repoapi
refactoring.
related to #2503918
Schema of the data
------------------
First take a look at the data schema_ then try to remember that you are browsing
through a heap of data by applying stylesheets to the results of queries. This
site is not a content management system with items placed in folders. It is an
interface to a database which applies a view to retreived data.
.. _schema: schema