sortedJson method
Returns a Json i.e. Map<String, dynamic>
representation of the BaseModel,
with the keys sorted alphabetically.
Implementation
Map<String, dynamic> sortedJson({
bool includeNulls = false,
}) {
final a = toJson(includeNulls: includeNulls);
final b = a.keys.toList(growable: false)
..sort((k1, k2) => k1.compareTo(k2));
final c = {for (var k in b) k: a[k] as dynamic};
return c;
}