refactor: add field to APIError struct

internal/handler/contact_handler.go

@@ -97,17 +97,23 @@ func (h *ContactHandler) create(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if contact.Name == "" {
-		BadRequest(w, ErrMissingRequired, RequiredFieldErr("name"))
+		err := ErrMissingRequired
+		err.Field = "name"
+		BadRequest(w, err, RequiredFieldErr("name"))
 		return
 	}
 
 	if contact.Company == "" {
-		BadRequest(w, ErrMissingRequired, RequiredFieldErr("company"))
+		err := ErrMissingRequired
+		err.Field = "company"
+		BadRequest(w, err, RequiredFieldErr("company"))
 		return
 	}
 
 	if contact.Phone == "" {
-		BadRequest(w, ErrMissingRequired, RequiredFieldErr("phone"))
+		err := ErrMissingRequired
+		err.Field = "phone"
+		BadRequest(w, err, RequiredFieldErr("phone"))
 		return
 	}