make ObjectMappers consistent across GraphQLResponse and GraphQLClients

[regulskimichal]

Pull request checklist

• [ ] Please read our contributor guide
• [ ] Consider creating a discussion on the discussion forum first
• [ ] Make sure the PR doesn't introduce backward compatibility issues
• [x] Make sure to have sufficient test cases

Pull Request type

• [x] Bugfix
• [ ] Feature
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Other (please describe):

Changes in this PR

Currently there is an issue related to the recent changes that induced GraphQLRequestOptions and refactoring of createCustomObjectMapper() method, that makes it impossible to use custom ObjectMapper during deserialization of data in GraphQLResponse

Alternatives considered

Describe alternative implementation you have considered