* Allow for dynamic feature flags
Giving more control over feature flags, allowing administrator to define
custom logic around whether features are enabled for particular users /
roles.
The exposed function can be used for things like:
* progressive rollout of features (1%, 5%, 50%, 100%)
* experimentation
* role-based feature affectation (only admins see a particular feature)
* fix build
* Addressing comments
* Addressing @hughhh's comments
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