Hash should optionally be included in the save model output

[krassowski]

Problem

Contents manager get() method now supports require_hash option and returns hash if queried with require_hash=True:

jupyter_server/jupyter_server/services/contents/filemanager.py

Line 412 in 74655ce

def get(self, path, content=True, type=None, format=None, require_hash=False):

however save() does not support require_hash and frontend needs to update the hash after each save leading to rather inelegant and resource-wasting frontend implementation:

this._manager.contents 
   .save(path, options) 
   .then(async contentsModel => { 
     const model = await this._manager.contents.get(path, { 
       content: false, 
       hash: true 
     }); 
     return { 
       ...contentsModel, 
       hash: model.hash, 
       hash_algorithm: model.hash_algorithm 
     } as Contents.IModel; 

Proposed Solution

Support require_hash in save() method of the contents manager (and expose it via REST API).

Additional context

This is the case since:

• Support get file(notebook) md5 #1363
• Change md5 to hash and hash_algorithm, fix incompatibility #1367