Updates an existing campaign.

The campaign must have finished preprocessing and be in a draft or scheduled status to be updated.

Automation templates passed in automation_templates are added to the ones already on the campaign. A template that is already on the campaign is skipped, so the request is safe to retry. Every template must belong to the organization and must not be archived; otherwise nothing is updated. To add automation templates to a campaign that has already been sent, use the Attach Automation Templates to Campaign endpoint.