Ability to add and handle index in JSON documents even though hierarchy has been added

[tedekeroth]

The ability to use hierarchies i Marten is great, but there are a few issues with it, one I would like to address here:

When an hierarchy is added in code, Marten then use the base class as the table, and all objects that are children of that base class is persisted into the same table. If there for example is this structure: CoreObject-->Actor-->Customer, and I add hierarchy, like this:

StoreOptions so = new StoreOptions();
so.Schema.For<CoreObject>().AddSubClassHierarchy();

all objects will be in the folder mt_doc_coreobject (which I would prefer not be the case, but that is another question).

The problem is that I can no longer, using Marten, create indexes in the JSON document that is of any of the subtypes; only on the basetype CoreObject, which in most cases isnt very good. There are for example Username in the Actor class, and a PopulationRegNbr in the Customer class that would need to be indexed:

    storeOptions.Schema.For<Customer>().Index(x => x.PopulationRegistryNumber); // won't work, index will not be created

So, I discussed ni the gitter chat with Jeremy Miller, and he suggested that I add this missing functionality as a feature request here on GitHub:

Suggestion: To support creating indexes for properties inside a JSON document when Marten has a hierarchy added, thus storing a number of different types in the same table.

With Regards,
Ted