POST /experimental/orgs/{orgId}/promotions/{campaignId}/activate

Activates a promotion offer for this org on behalf of the signed-in user, who must be a member of the org and eligible for the offer. The org in the path receives what the offer grants. Once per user: each member may activate it once, for one of their orgs, and a second activation by the same user, in any org, grants nothing and returns activated. An activation by a colleague does not count against the user. Returns 404 for an unknown campaign, and 403 for a user who is not a member or not eligible, and for an API key.