Create table lever mapper, rather than just column level mapping

Hi, for a column mapping we can have a type mapper to convert from an interface to a concrete type, like in the instance of a json column we can map that. But we cannot do this for a whole table, we cannot have a table mapping that uses an interface, rather than the concrete type.

In our solution we have heavily modularised into specific types/related types series of projects, and each module has a provider which deals with it's own queries to the database. Using the concrete type here is all good when it is the same module. The problem comes when we have a more complex module that uses types from other modules. We only expose interfaces outside of these module projects and do not want to reference projects that have the concrete instances.

So how could we do something similar to a column mapping but for a table so we can map an interface to a concrete type? That way we can supply the table mapping in some form and register it in our concrete modules project leaving the complex mapping to only need reference the interface. Obviously underneath this table mapping, it would need individual column mappings for all of it's types as usual.

The issue names no files, tests, or entry points. Start by locating the existing column-level type-mapping and mapping-registration code; done means a table-level mapping can associate an interface with a concrete type while retaining individual column mappings.