The login name is added to the user context node. The name is accessable via
ssp template by using the context node
(e.g. context/platform("user")/platform("userName")).
Returns a GraphNode containing user context information in
addition to the information already existing in the provided
GraphNode.
The information previously existing in the provided GraphNode
are not changed by this method.
The method may add the context information directly to the provided
GraphNode or create a new GraphNode instance,
in the latter the returned GraphNode must be modifiable.
In both cases the resulting GraphNode is returned by the
method.