Add replay protection feature

[agbaraka]

Hello Team.

Kindly assist to review this initial implementation of App Check Replay Protection API as requested in issue #632

Your feedback and guidance will be highly appreciated.

[google-cla]

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[weixifan]

Thank you for this contribution! I have left comments addressing App Check domain-specific concerns, but I will leave it to other reviewers to address Go language style and library use concerns.

[agbaraka]

Hi @weixifan and @lahirumaramba

Thank you for taking your time to review this implementation. Your guidance on this is much appreciated.

I have update the implementation as per @weixifan recommendations. Please review and advise.

Happy coding

[agbaraka]

Hi @weixifan. I hope all is well.

I have refactor token verifier url generation as recommended. I agree, It looks cleaner than before.

Please review

Thanks

[agbaraka]

Hi @weixifan and @lahirumaramba.

Any feedback on this PR?

[weixifan]

Sorry about the delay. This is approved from App Check's point of view. A Golang reviewer will review your PR for style and consistency with existing code.

Thank you for your contribution!