Bumped up Dart min version to 3.0.0 for json_serializable

[al-kimmel-serj]

Bumped up Dart min version to 3.0.0 for json_serializable, because json_serializable requires Dart 3.5 since 6.9.0.

Error out about bump up Dart version has been added to json_serializable release 6.9.3

@jaumard @josh-burton @amondnet @sbu-WBT @kuhnroyal @agilob @ahmednfwela, could you review my PR?

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[wing328]

thanks for the PR

please follow step 3 to update the samples.

[al-kimmel-serj]

thanks for the PR

please follow step 3 to update the samples.

@wing328, thank you. I've updated samples in PR.

[wing328]

thanks for the PR

does it mean the output (dart API client) no longer work with Dart 2.x?

[al-kimmel-serj]

Yes. I use json_serializable as serializationLibrary and I see error when I try to generate code via dart run build_runner build with json_serializable:6.9.0. Here is example of error:

line 18, column 30 of .: Expected to find ')'.
   ╷
18 │         if (instance.message case final value?) 'message': value,
   │                              ^^^^
   ╵

json_serializable generates code with case clauses in if statements since 6.9.0.

[wing328]

what about adding an option supportDart2 (default to false) for backward compatibility?

we can't ship a change that breaks all Dart 2.x users.