Improving GraphQL type handling and upgrading testng

[manikandan-ravikumar]

Partial update to entities

The purpose of this PR is to enable updation of selective entity fields. By introducing Optional, it also differentiates null from undefined

Let's assume an entity with 5 fields and the requirement is to update only one field to null. We can set the value of that field to null and omit other fields in a mutation query.

Changelog

• Fixing import issues with javax.xml.bind.DatatypeConverter
• Bump testng version from 6.9.10 to 7.4.0
• New GraphQLUndefined type
• Following improvements in MethodDataFetcher:
  1. Improved Nullable handling using Optional
  2. Handle Optional field types
  3. Support RawType in additional to WrpperType
• GraphQLInputTest updated to test Optional field types in GraphQL queries