add int type support for lengthEqual validator

Author: Raif Özdoğan

packages/form_builder_validators/lib/src/form_builder_validators.dart

@@ -156,9 +156,11 @@ class FormBuilderValidators {
     return (T? valueCandidate) {
       assert(valueCandidate is String ||
           valueCandidate is Iterable ||
+          valueCandidate is int ||
           valueCandidate == null);
       var valueLength = 0;
 
+      if (valueCandidate is int) valueLength = valueCandidate.toString().length;
       if (valueCandidate is String) valueLength = valueCandidate.length;
       if (valueCandidate is Iterable) valueLength = valueCandidate.length;
 

packages/form_builder_validators/test/form_builder_validators_test.dart

@@ -192,6 +192,22 @@ void main() {
             expect(validator("4444"), isNotNull);
           }));
 
+  testWidgets(
+      'FormBuilderValidators.lengthEqual for int',
+      (WidgetTester tester) => testValidations(tester, (context) {
+            final validator = FormBuilderValidators.lengthEqual<int>(3);
+
+            // Pass
+            expect(validator(333), isNull);
+
+            // Fail
+            expect(validator(null), isNotNull);
+            expect(validator(0), isNotNull);
+            expect(validator(1), isNotNull);
+            expect(validator(22), isNotNull);
+            expect(validator(4444), isNotNull);
+          }));
+
   testWidgets(
       'FormBuilderValidators.email',
       (WidgetTester tester) => testValidations(tester, (context) {