added fromJson factory methods to RangeOfAqi, and to RangeOfAqiValue data models.

lib/pages/analytics/models/range_of_aqi.dart

@@ -9,6 +9,15 @@ class RangeOfAqi extends Equatable {
     required this.date,
   });
 
+  factory RangeOfAqi.fromJson(Map<String, dynamic> json) {
+    return RangeOfAqi(
+      date: DateTime.parse(json['date'] as String),
+      data: (json['data'] as List<dynamic>)
+          .map((e) => RangeOfAqiValue.fromJson(e as Map<String, dynamic>))
+          .toList(),
+    );
+  }
+
   @override
   List<Object?> get props => [data, date];
 }
@@ -26,6 +35,15 @@ class RangeOfAqiValue extends Equatable {
     required this.max,
   });
 
+  factory RangeOfAqiValue.fromJson(Map<String, dynamic> json) {
+    return RangeOfAqiValue(
+      type: json['type'] as String,
+      min: (json['min'] as num).toDouble(),
+      average: (json['average'] as num).toDouble(),
+      max: (json['max'] as num).toDouble(),
+    );
+  }
+
   @override
   List<Object?> get props => [type, min, average, max];
 }