SOAP API is deprecated for Conga Contracts.
Each class has an id field, which is defined as the UUID of a specific object. When creating new objects, this field must be blank and it will be generated by the server. When modifying an object retrieved via a query, it must not be changed in order to have an update function correctly. However, setting the id to null and using create on the object is a convenient way to either duplicate objects, or use existing objects as a template for creating new ones.