WorkflowDefinition
    graph       WorkflowGraph
    scope       WorkflowInstanceScope'
    name        (CI Text)
    UniqueWorkflowDefinition name scope

WorkflowInstance
    definition  WorkflowDefinition
    graph       (WorkflowGraph Int64 Int64)  -- FileId, UserId
    scope       (WorkflowInstanceScope Int64 Int64 Int64)  -- TermId, SchoolId, CourseId
    name        (CI Text)
    category    (CI Text) Maybe
    UniqueWorkflowInstance name scope

WorkflowWorkflow
    instance    WorkflowInstance
    graph       WorkflowGraph
    initiator   UserId Maybe
    payload     WorkflowPayload
    currentNode WorkflowGraphNodeLabel Maybe