Refactor http body parsing

Resolves the issue: [Bug] expirationDate failed to be parsed by Gson

1. Move the parsing logic of the HttpResponse#body field to a separate class.
2. Replace gson->jackson
3. Encapsulate the internal implementation of the parsing so that clients will not be affected if any low-level changes happen in the parsing logic.

Changes include

• Refactoring
• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• Added Unit Tests, wherever applicable.
• Updated the Readme
• Existing Tests pass: The test shouldSuccessfullySerializeLegalTag is breaking in the existing code.
• Verified functionality locally
• Self Reviewed my code for formatting and complex business logic.