idea: provide a query service that returns a user's DAG

[SteVwonder]

@tanimislam has a tool, epithet, that uses the various CLI tools of Slurm to reverse-engineer the DAG of a given user's jobs. It would be great if Flux's depend module provided this DAG via an easily consumable interface, to avoid having to reverse engineer dependencies from individual jobspecs.

EDIT: bonus points for interfacing with epithet or providing our own front-end tool that can visualize the DAG

[tanimislam]

Had a conversation with Francesco di'Natale a few days ago. Apparentlymaestro status does something similar to epithet. He also mentioned that maestro could use flux as a backend for its status information without significant effort.