[FEATURE] Implement ResolveAll endpoint for bulk evaluation

[L3o-pold]

Requirements

Following open-feature/flagd#239

documentation: https://github.com/open-feature/flagd/blob/febc0cf2caa4f728320a613c8704068f336315db/docs/usage/evaluation_examples.md#resolve-all-values

[beeme1mr]

Hey @L3o-pold, how do you envision this working? I'm not sure how you'll be able to access the bulk API since the PHP SDK complies with the dynamic context paradigm. Perhaps a more performant option could be adding in-process support.

[L3o-pold]

I am not sure to fully understand what it implies, but our usecase is to resolve all the flags based on the provided context when needed. Is that not working as implemented?

For example on user login, I want to query all the features enabled for the user instead of querying every feature/ flag one by one.