Check the key/value pair and return null if it is valid or a reason string if there is a validation failure. The null type for success is used to avoid allocations or other overhead since the validation checks tend to be a hot path.
Check the key/value pair and return null if it is valid or a reason string if there is a validation failure. The null type for success is used to avoid allocations or other overhead since the validation checks tend to be a hot path.