docs: Added dynamic reference documentation

Author: Gustavo Mendonça

docs/tutorials/mongoose.md

@@ -127,6 +127,14 @@ Be wary of circular dependencies. Direct references must be declared after the r
 
 <<< @/docs/tutorials/snippets/mongoose/virtual-references.ts
 
+### Dynamic References
+
+`@tsed/mongoose` supports `mongoose` dynamic references between defined models.
+
+This works by having a field with the referenced object model's name and a field with the referenced field.
+
+<<< @/docs/tutorials/snippets/mongoose/dynamic-references.ts
+
 ## Register hook
 
 Mongoose allows the developer to add pre and post [hooks / middlewares](http://mongoosejs.com/docs/middleware.html) to the schema. 

docs/tutorials/snippets/mongoose/dynamic-references.ts

@@ -0,0 +1,11 @@
+import {Model, Ref, DynamicRef} from "@tsed/mongoose";
+import {Enum, Required} from "@tsed/common"
+
+@Model()
+export class DynamicRef {
+    @DynamicRef('type')
+    dynamicRef: Ref<ModelA | ModelB>
+
+    @Enum(['Mode lA', 'ModelB']) 
+    type: string // This field has to match the referenced model's name
+}