You can use the API to send a POST request to the document command service. Use the c parameter for that with the info value and the key parameter identifying the document you want to find the information about. The parameters are sent as a part of the JSON object in the request body:
In case the document is being edited, for instance, by two users, the document editing service will respond with the following information:
"users": ["6d5a81d0", "78e1e841"]
- key is the identifier of the document (the same as in the POST request above);
- status with value of 1 means that the document is currently being edited;
- and the users is the array of the IDs of the users who take part in the co-editing.
Further information about the response from the document editing service can be found at this page.