JIRA: https://jira.spring.io/browse/INT-4037 Provide type information in `LinkNode`s, input, output, error, discard. This might be rendered as: ``` +---(discard) | +----o----+ | | | | | | (input)--o o---(output) | | | | | | +----o----+ | +---(error) ``` "links" : [ { "from" : 10, "to" : 9, "type" : "output" }, { "from" : 10, "to" : 1, "type" : "error" } ] Document `link.type` in the `graph.adoc`