refactor(core): destructure core folder and reintegrate extensions

lib/database/models/external_module.dart

@@ -0,0 +1,37 @@
+import 'package:lunasea/core.dart';
+
+part 'external_module.g.dart';
+
+@JsonSerializable()
+@HiveType(typeId: 26, adapterName: 'LunaExternalModuleAdapter')
+class LunaExternalModule extends HiveObject {
+  @JsonKey()
+  @HiveField(0)
+  String displayName;
+
+  @JsonKey()
+  @HiveField(1)
+  String host;
+
+  LunaExternalModule({
+    this.displayName = '',
+    this.host = '',
+  });
+
+  @override
+  String toString() => json.encode(this.toJson());
+
+  Map<String, dynamic> toJson() => _$LunaExternalModuleToJson(this);
+
+  factory LunaExternalModule.fromJson(Map<String, dynamic> json) {
+    return _$LunaExternalModuleFromJson(json);
+  }
+
+  factory LunaExternalModule.clone(LunaExternalModule profile) {
+    return LunaExternalModule.fromJson(profile.toJson());
+  }
+
+  factory LunaExternalModule.get(String key) {
+    return LunaBox.externalModules.read(key)!;
+  }
+}