Add FGA client to support FGA endpoints (#353)

* Fix typo for IdempotencyKey json encoding

* Add FGA client and methods

* Add object types list and batch update methods

* Add Authorized method to CheckResponse and return CheckResponse from all check methods

* Make ObjectId required for UpdateObjectOpts

* Update FGA tests

* Rename Warrants field to Checks

* Update CheckResponse to include DebugInfo struct

* Rename BatchCheck to CheckBatch

* Remove single check method and rename CheckMany to Check

* Rename Warrants field to Checks

* Rename fga Object to Resource

* Update json encoding for checks

* Update CheckResultAuthorized constant to be lowercase and add new CheckResultNotAuthorized constant

* Add constants for Warrant create/delete operations + add constants for check operations ('any_of', 'all_of', etc).

* Fix grammar in resource comments

* Implement EncodeValues for Context type

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Co-authored-by: Karan Kajla <karan@warrant.dev>

Author: stanleyphu