FK Support

[Reshiru]

[OzBob]

A recent post from Steve Sandersion mentioned this issue: "capability already exist in the underlying TG.Blazor.IndexedDB package, it’s probably quite feasible for them to be surfaced through Reshiru’s
DB context APIs" from post in https://blog.stevensanderson.com/2019/08/03/blazor-indexeddb/

and

"StoreSchema ... a set of foreign key indexes" "IndexSpec is used to define the primary key and any foreign keys that are required." from https://github.com/wtulloch/Blazor.IndexedDB