Create a flow

Creates a DRAFT from a definition (see GET /flows/nodes for the catalogue). The definition is validated first: structure, per-node config, the plan's node cap, channel compatibility with the trigger source, keyword collisions with active flows, and references to custom fields, comment triggers and other flows (422 invalid_definition with errors[] and warnings[]). Nothing runs until you publish and activate. The visual builder lays the nodes out the first time the flow is opened. Requires the write scope.