update inputfile for dart and flutter

Author: lohanidamodar

templates/dart/lib/src/input_file.dart.twig

@@ -6,11 +6,35 @@ class InputFile {
   final String? filename;
   final String? contentType;
 
-  /// Provide a file, use `path` for IO platforms
-  /// and provide `bytes` for web platform
-  InputFile({this.path, this.filename, this.contentType, this.bytes}) {
+  InputFile._({this.path, this.filename, this.contentType, this.bytes}) {
     if (path == null && bytes == null) {
-      throw {{ spec.title | caseUcfirst }}Exception('One of `path` or `bytes`  is required');
+      throw AppwriteException('One of `path` or `bytes`  is required');
     }
   }
+
+  /// Provide a file using `path`
+  factory InputFile.fromPath({
+    required String path,
+    String? filename,
+    String? contentType,
+  }) {
+    return InputFile._(
+      path: path,
+      filename: filename,
+      contentType: contentType,
+    );
+  }
+
+  /// Provide a file using `bytes`
+  factory InputFile.fromBytes({
+    required List<int> bytes,
+    required String filename,
+    String? contentType,
+  }) {
+    return InputFile._(
+      bytes: bytes,
+      filename: filename,
+      contentType: contentType,
+    );
+  }
 }