dart: remove dep on dartson's TypeTransformer for enums

Author: while-loop

modules/swagger-codegen/src/main/resources/dart-jaguar/enum.mustache

@@ -1,6 +1,5 @@
 part '{{classFilename}}.jser.dart';
 
-@Entity()
 class {{classname}} {
   /// The underlying value of this enum member.
   final {{dataType}} value;
@@ -17,14 +16,12 @@ class {{classname}} {
   {{/allowableValues}}
 }
 
-class {{classname}}TypeTransformer extends TypeTransformer<{{classname}}> {
+class {{classname}}TypeTransformer {
 
-  @override
   dynamic encode({{classname}} data) {
     return data.value;
   }
 
-  @override
   {{classname}} decode(dynamic data) {
     switch (data) {
       {{#allowableValues}}

modules/swagger-codegen/src/main/resources/dart/enum.mustache

@@ -1,4 +1,3 @@
-@Entity()
 class {{classname}} {
   /// The underlying value of this enum member.
   final {{dataType}} value;
@@ -15,14 +14,12 @@ class {{classname}} {
   {{/allowableValues}}
 }
 
-class {{classname}}TypeTransformer extends TypeTransformer<{{classname}}> {
+class {{classname}}TypeTransformer {
 
-  @override
   dynamic encode({{classname}} data) {
     return data.value;
   }
 
-  @override
   {{classname}} decode(dynamic data) {
     switch (data) {
       {{#allowableValues}}