[dart][dart-dio] Raise min Dart to 2.7.0 & update built_value constraint (#8684)

* raise min Dart version to 2.7.0 / Flutter 1.12.0
* update constraints for built_value to support new major versions with null safety

Author: kuhnroyal

modules/openapi-generator/src/main/resources/dart-dio/README.mustache

@@ -19,7 +19,7 @@ For more information, please visit [{{{infoUrl}}}]({{{infoUrl}}})
 
 ## Requirements
 
-Dart 1.20.0 or later OR Flutter 0.0.20 or later
+Dart 2.7.0 or later OR Flutter 1.12 or later
 
 ## Installation & Usage
 

modules/openapi-generator/src/main/resources/dart-dio/header.mustache

@@ -1,6 +1,6 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import

modules/openapi-generator/src/main/resources/dart-dio/pubspec.mustache

@@ -2,16 +2,16 @@ name: {{pubName}}
 version: {{pubVersion}}
 description: {{pubDescription}}
 environment:
-    sdk: ">=2.6.0 <3.0.0"
+    sdk: ">=2.7.0 <3.0.0"
 dependencies:
     dio: ^3.0.9
-    built_value: ^7.1.0
-    built_collection: ^4.3.2
+    built_value: ">=7.1.0 <9.0.0"
+    built_collection: ">=4.3.2 <6.0.0"
 {{#timeMachine}}
     time_machine: ^0.9.12
 {{/timeMachine}}
 dev_dependencies:
-    built_value_generator: ^7.1.0
+    built_value_generator: ">=7.1.0 <9.0.0"
     build_runner: ^1.7.1
     test: ^1.3.0
 

samples/client/petstore/dart-dio/petstore_client_lib/README.md

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import
 

samples/client/petstore/dart-dio/petstore_client_lib/lib/api.dart

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import
 

samples/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import
 

samples/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import
 

samples/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import
 

samples/client/petstore/dart-dio/petstore_client_lib/lib/api_util.dart

@@ -1,7 +1,7 @@
 //
 // AUTO-GENERATED FILE, DO NOT MODIFY!
 //
-// @dart=2.6
+// @dart=2.7
 
 // ignore_for_file: unused_import