remult.isAllowed should also support @BackendMethod

[noam-honig]

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In have a Backend method where it's allowed options determines who is allowed to run it:

@BackendMethod({ allowed: Allow.authenticated })

In the frontend, I would like to display the button only to users who can run the BackendMethod.
Today the only way I can do that, requires me to repeat myself and write:

remult.isAllowed(Allow.authenticated)

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I would prefer to have a single source of truth, meaning that if I defined the rule once in the backend method, I should be able to query it using something like:

remult.isAllowed(TasksController.setAll)

and that it'll take into consideration the allowed: AllowAuthenticated
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