Business applications can use this service API to add placeholder to a workflow in a package.  A place holder is required when you do not know the identity of the intended recipient in a workflow.

Note the placeholder will be added as the last user in the workflow.  Hence further work may be required to remove a current user/group, already present in the workflow.

Adding a place holder allows you to proceed and add signature and/or input fields to the document, which can then be assigned to individual users at a later stage. While XML type document preparation, only supported role types are "SIGNER", "REVIEWER" and "CARBON_COPY"

https://api.signinghub.com/v3/packages/{package_id}/workflow/placeholder
HTTP Verb		POST
Authorization		Bearer {access_token}
Content-Type		application/json
Accept		application/json
Response Headers
Request Body		[    {       "placeholder": "Customer 1",       "role": "SIGNER",       "email_notification": true,         "signing_order": 1    } ]
Status Code	Message	Response Body
200	OK
400	Bad Request	{   "Message": "Recipient role is not supported for an XML type document" }
403	Forbidden	{   "Message": "You are not allowed to perform this action on locked workflow" }
		{    "Message": "Account is disabled" }
		{   "Message": "You are not allowed to perform the requested operation" }
500	Internal Server Error	{   "Message": "An internal server error occurred while processing the request" }