Creates a new future by applying the given function to this future, in future -- when this future is completed.
The returned object of the function may or may not be directly used. Depending on the internal implementation, A new future object will be created with the value or exception of it and returned, instead of returning it directly.
If the function returns not a Future but a Result, the result is mapped to a future.
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a function applied to this result |
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[Future<A>] the new future |