Reads a Option[T] search optional or nullable field at JsPath (field not found or null is None
and other cases are Error).
It runs through JsValue following all JsPath nodes on JsValue except last node:
- If one node in JsPath is not found before last node => returns JsError( "missing-path" )
- If all nodes are found till last node, it runs through JsValue with last node =>