[Thien] Create PostgrestResponse class and PostgrestError class 🥳

[duythien0912]

What kind of change does this PR introduce?

This PR to create a feature request in #4 It has 2 new class in the folder:

• lib/models/postgrest_error.dart
• lib/models/postgrest_response.dart

And change code on lib, example, test to have a response with custom class PostgrestResponse. Have been move statusCode to PostgrestError.code

What is the current behavior?

4

What is the new behavior?

Additional context

All tests passed on folder test Not test example/main.dart yet

[duythien0912]

@phamhieu I just

• Clean up code
• Add function postgrestResponseFromJson, postgrestErrorFromJson 🙌

[duythien0912]

I just fixed the "stored procedure" test case already ^^