feat(appsync): Add new service AppSync

[MarioRgzLpz]

Context

In order to cover more checks, we need to create a new AWS service for AppSync. This new service will allow for the implementation of additional checks.

Description

Add new appsync_service with respective unit tests.

Checklist

• Are there new checks included in this PR? No
  • If so, do we need to update permissions for the provider? Please review this carefully.
• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.84%. Comparing base (bc308de) to head (25eda2b).
Report is 47 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5589      +/-   ##
==========================================
+ Coverage   89.75%   89.84%   +0.09%     
==========================================
  Files        1095     1117      +22     
  Lines       33973    34608     +635     
==========================================
+ Hits        30491    31093     +602     
- Misses       3482     3515      +33     

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