Saving a file should involve only one API request

[krassowski]

Description

Since #15577 two requests are performed when saving the file:

• save
• get new model (hash without content)

jupyterlab/packages/docregistry/src/context.ts

Lines 753 to 765 in 35bab6e

	return 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;
	});

Expected behavior

Instead of the second request, the hash should be extracted from the save response. Depends on:

• Hash should optionally be included in the save model output jupyter-server/jupyter_server#1453

Context

• JupyterLab version: 4.1.0 - 4.3.0beta0