PUT Project Custom Field
PUT /admin/project/{projectId}/customfield/{customFieldName}
Add a new custom field to a specific project.
PUT /rest/admin/project/{projectId}/customfield/{customFieldName}?{emptyFieldText}Sample
PUT /rest/admin/project/CMN/customfield/Region?emptyFieldText=<no region>&bundle=RegionEnumEmpty Response.
Response code: 201
Response message: CreatedLast modified: 2 February 2017