Support for custom discriminator in EF Stores

[etiennecl]

It would be very useful if the EF Store could use a custom discriminator for the Type column. The reason why is because right now it uses the assembly qualifier name although during the lifetime of a codebase it can happen that we reorganize the folder structure/namespace, therefore, the Factory will throw because it will not be able to create a new instance of an unknown type.

Something like JsonSubTypes could be very useful.

[lucabriguglia]

I agree with you, this is a feature that we should add.