署名者の本人確認

curl -i -X POST "https://api.box.com/2.0/sign_requests" \
     -H "authorization: Bearer <ACCESS_TOKEN>" \
     -H "content-type: application/json" \
     -d '{
       "parent_folder": {
         "type": "folder",
         "id": "0987654321"
       },
       "source_files": [
         {
           "type": "file",
           "id": "123456789"
         }
       ],
       "signers": [
         {
           "email": "signer@example.com",
           "role": "signer",
           "password": "example-password",
           "verification_method": {
             "type": "phone",
             "phone_number": "+15551232190"
           }
         }
       ]
     }'