Process declaration of access strategy. Gives new access strategy checker_function and item_sensitive from declaration.
@param {object} delcaration - is an object with attributes:
name - string, required. The name of the access strategy - it has to be a string unique amongst any other access strategies in your application.
checker_function - function, required. It’s a function that takes a context instance as an argument and implements the logic of the access strategy. Its return values can be:
* boolean - true for granting the access and false for denying.
* a Promise - that resolves when the access is granted and rejects otherwise. Use promises only when the decision depends on a result of an asynchronous function.
item_sensitive - boolean, defaults to false. If set to true, the checker_function is provided with a second argument, which contains an object representing the resource being requested.