perf(keto-client-wrapper): improve AuthorizationGuard performance by combining permission checks

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The Ory Keto PermissionApi contains a batchCheckPermission (why did I miss it?).
It could be used to run all permissions checks in a single request, which would offer great performance improvements for nested conditions!

1. Find a way to flatten the conditions without losing the requirement info
2. Resolve the tuple's templates
3. Run the batchCheckPermission
4. Compare the results (Array<{ allowed: boolean, error?: string }>) based on the array index.

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I understand why I missed it. It is a very recent addition, see this changelog.
It might not yet be available in the HTTP API...

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I need to wait for the new release of Ory Keto on GitHub and Docker Hub.