Follow up from #201

Recently you added the IxxxApiClient interfaces, to allow each client to be re-implemented as per specific requirements. However, I didn't want to have to re-implement everything you had done, just to add some extra methods.

In the case of the EF core provider, patching a document via "class" is difficult, as everything is being interrogated and built-up at runtime. I don't know which properties will have been changed, so I would need an entirely dynamic way to build the patch objects. I did consider, and attempt, using things like an expando object, but realistically the easiest way to handle it is to be able to construct the patch json directly.

Side note: I am basing the ArangoDB EF core provider on the existing cosmos provider that is currently available, and this is the approach they also follow.

Back on topic.... therefore I wanted to use all the standard functionality, but just add an additional PatchDocument method, that allowed me to pass in the pre-json'ed patch document.

With that in mind, I standardised each client class, and then provided access to the various underlying services via protected properties, and made all the operations virtual. Then I can take your default implementation and just adjust it to my requirements, rather than copying all your code just to add one method.