feat: created_via for tracking how runners got into the system (#212)

close #211

squash merge please:)

Reviewed-on: #212

src/models/responses/ResponseParticipant.ts

@@ -50,6 +50,12 @@ export abstract class ResponseParticipant implements IResponse {
     @IsString()
     email?: string;
 
+    /**
+     * how the participant got into the system
+     */
+    @IsString()
+    created_via?: string;
+
     /**
      * The participant's address.
      */