Add foreignkey and secure for foreignkey support to databse module.

[saeedtabrizi]

Hi @rosko @icebob ,
As I see in the following line there is no support for secure foreignkey or foreignkey in database module .
So when we store the ObjectId as string in mongodb , developers must use decode and encode methods to handle this logic , That is harmful .

database/src/methods.js

Line 488 in e1ac4da

if (this.$primaryField.secure) id = this.encodeID(id);

I recommend to support foreignkey in field definition and enable secure functionality over that .