post https://api.gathercontent.com/v0.5/items//apply_template
Applies the structure of a Template to an existing Item.
Beware that, just like within the application, this action will override the existing structure of an Item and may result in loss of content when fields do not match. Ensure you take necessary precautions.
Not supported in upgraded Content Editor accounts
Accounts that have been upgraded to the new Content Editor will not be able to apply templates to items using this endpoint and will receive a 400 error.