🥅 Throw argument error with invalid baseUrl (#2127)

Provide a readable error when the `baseUrl` is not matching the
condition.

### New Pull Request Checklist

- [x] I have read the
[Documentation](https://pub.dev/documentation/dio/latest/)
- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
conflicts (via merge from master or rebase)
- [ ] I have added the required tests to prove the fix/feature I'm
adding
- [ ] I have updated the documentation (if necessary)
- [x] I have run the tests without failures
- [ ] I have updated the `CHANGELOG.md` in the corresponding package

dio/lib/src/options.dart

@@ -99,7 +99,13 @@ mixin OptionsMixin {
   late String _baseUrl;
 
   set baseUrl(String value) {
-    assert(value.isEmpty || kIsWeb || Uri.parse(value).host.isNotEmpty);
+    if (value.isNotEmpty && !kIsWeb && Uri.parse(value).host.isEmpty) {
+      throw ArgumentError.value(
+        value,
+        'baseUrl',
+        'Must be a valid URL on platforms other than Web.',
+      );
+    }
     _baseUrl = value;
   }
 

dio/test/options_test.dart

@@ -482,7 +482,7 @@ void main() {
       if (kIsWeb) 'api/',
     ];
     for (final url in invalidUrls) {
-      expect(() => BaseOptions(baseUrl: url), throwsA(isA<AssertionError>()));
+      expect(() => BaseOptions(baseUrl: url), throwsA(isA<ArgumentError>()));
     }
     for (final url in validUrls) {
       expect(BaseOptions(baseUrl: url), isA<BaseOptions>());