Serializes a map as an array of key-value objects.
Serializes a map as an array of key-value objects.
Note that spray-json's JsonFormat for maps has the same signature, so if you need to use both at the same time,
you need to extend the DefaultJsonProtocol trait instead of importing it.
the type of the keys of the map
the types of the value of the map
an instance of RootJsonFormat for the map