Следующий код работал для меня:
def response = httpRequest(acceptType: 'APPLICATION_JSON', contentType: 'APPLICATION_ZIP',
customHeaders : [[name: "authorization" , value : "${authToken}"],[name: 'x-username' , value: 'admin']],
httpMode: 'POST', ignoreSslErrors: true,
multipartName: '<fileName>', timeout: 900,
responseHandle: 'NONE', uploadFile: "<filePath>",
url: "${url}")