Added support for required field in queries

[xuewei8910]

TODO:

• [ ] Update CHANGELOG.md* with your change (include reference to issue & this PR)
• [ ] Make sure all of the significant new logic is covered by tests
• [ ] Rebase your changes on master so that they can be merged easily
• [ ] Make sure all tests and linter rules pass

*Make sure changelog entries note which project(s) has been affected. See older entries for examples on what this looks like.

[apollo-cla]

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