NewMapOpts creates a new MapOpts with the specified map of values and an optional validator.

NewNamedMapOptions creates a reference to a new NamedMapOpts struct.

BoolOptions member functions with external access do not require locking by the caller, while functions with internal access presume the caller to have taken care of any locking needed.

MapOptions holds a map of values and a validation function.

NamedMapOptions is a MapOptions struct with a configuration name.

Option is the structure used to specify the semantics of a configurable boolean option.

ChangedFunc is called by `Apply()` for each option changed.

Validator returns a validated string along with a possible error.

VerifyFunc validates option key with value and may return an error if the option should not be applied.