Start a campaign

Starts (or resumes) the campaign. Requires an active subscription. All start checks are run and the first failing one is returned with a stable code (see the examples and the ErrorCode schema): identities, accounts connected, email versions with content and subject, LinkedIn daily ceiling, 1 to 30,000 recipients, at least one contact reachable on each channel used. A planned start, if any, is cancelled. Scheduling of contacts happens asynchronously after the response.