fix(server): correctly identify integers

mobile/openapi/lib/model/on_this_day_dto.dart

@@ -17,7 +17,7 @@ class OnThisDayDto {
   });
 
   /// Minimum value: 1
-  num year;
+  int year;
 
   @override
   bool operator ==(Object other) => identical(this, other) || other is OnThisDayDto &&
@@ -46,7 +46,7 @@ class OnThisDayDto {
       final json = value.cast<String, dynamic>();
 
       return OnThisDayDto(
-        year: num.parse('${json[r'year']}'),
+        year: mapValueOfType<int>(json, r'year')!,
       );
     }
     return null;