Provide methods to get the headers and raw response from OpenFgaClient methods

[rhamzeh]

Checklist

• I agree to the terms within the OpenFGA Code of Conduct.

Describe the problem you'd like to have solved

As a user, I'd like to be able to get the response headers when using OpenFgaClient

Describe the ideal solution

OpenFgaClient responses should have the equivalent of the following methods (naming as appropriate per language):

• GetHeaders(): Allows the user to get the response headers
• GetRawResponse(): Allows the user to get the raw response

Batch Methods such as non transactional Write and BatchCheck would have these methods on individual responses.

When possible, we should add these on the methods exposed by OpenFgaApi directly

Alternatives and current workarounds

No response

References

• JS SDK
• Go SDK
• .NET SDK
• Python SDK: Python SDK should provide a method for users to get the response headers and the raw response python-sdk#74
• Java SDK

Additional context

No response