refactor: network type handling to use a dedicated NetworkType extension type

Author: Egor Komarov

lib/app/service/assets_service.dart

@@ -234,7 +234,7 @@ class AssetsService {
     try {
       if (transport.transport.disposed) return null;
 
-      if (transport.networkType == 'ton') {
+      if (transport.networkType == NetworkType.ton) {
         final details = await JettonWallet.getJettonRootDetails(
           transport: transport.transport,
           tokenRoot: rootTokenContract,

lib/app/service/connection/connection.dart

@@ -4,5 +4,4 @@ export 'default_network.dart';
 export 'generic_token_subscriber.dart';
 export 'group.dart';
 export 'mapping/mapping.dart';
-export 'network_type.dart';
 export 'transport_strategies/transport_strategies.dart';

lib/app/service/connection/connection_service.dart

@@ -130,7 +130,7 @@ extension TransportTypeExtension on TransportStrategy {
       return (this as CommonTransportStrategy).networkType;
     }
 
-    return '';
+    return NetworkType.empty();
   }
 
   NetworkGroup get networkGroup {
@@ -157,8 +157,8 @@ extension TransportTypeExtension on TransportStrategy {
     return null;
   }
 
-  bool get isEverscale => networkType == 'ever';
-  bool get isVenom => networkType == 'venom';
-  bool get isTon => networkGroup.startsWith('ton');
+  bool get isEverscale => networkType.isEver;
+  bool get isVenom => networkType.isVenom;
+  bool get isTon => networkType.isTon;
   bool get isHmstr => networkGroup.startsWith('hmstr');
 }

lib/app/service/connection/data/connection_data/connection_data.dart

@@ -1,4 +1,4 @@
-import 'package:app/app/service/connection/network_type.dart';
+import 'package:app/app/service/connection/data/network_type.dart';
 import 'package:app/utils/utils.dart';
 import 'package:freezed_annotation/freezed_annotation.dart';
 import 'package:uuid/uuid.dart';