MockResponse class code is repeted in many NApps

[Rogerio Motitsuki]

As addressed by @ajoaoff in #24 (comment) the class MockResponse "is repeated over and over on all NApps and should consider using an external library for this, like https://github.com/getsentry/responses or https://requests-mock.readthedocs.io/en/latest/"

[Vinicius Arcanjo]

This MockResponse is not longer needed. It was addressed on PR #97