Support optional farm in CreateElementsWorkflow

An optional farm_id attribute must be available on CreateElementsWorkflow, to allow users to select a specific farm.

Depends on https://gitlab.com/arkindex/ponos/-/issues/99

added 1 deleted label

mentioned in issue frontend#568 (closed)

mentioned in merge request !1250 (merged)

closed with commit dbfe952f

mentioned in commit dbfe952f