Session states - Connector API

State	Description	Allowed actions
`UPLOADING`	Accepting data	ingest, `start-upload`, `delete`
`STARTED`	Connector is running	`terminate`
`DONE`	Connector finished	`initialize-session` (new session; `delete` returns `409`)

`GET /status` fields

Field	Description
`session_status`	Current state
`entities`	Uploaded entities (task-type names)
`upload_tasks_finished`	Background S3 writes completed
`can_upload_entities`	Ingest allowed
`can_start_upload`	`start-upload` allowed
`can_terminate`	`terminate` allowed

terminate — stop Connector, return to UPLOADING (more uploads allowed)
delete — remove files and session (UPLOADING only); returns 409 if status is DONE or STARTED