react-admin: [v4 beta] The "save" text is not translated but shown as a key: `ra.action.save`

What you were expecting:

The SAVE button to show the word Save

What happened instead:

The SAVE button shows the word ra.action.save

Steps to reproduce:

Just start a CREATE action for any resource and look at the “Save” button’s text:

Related code:

• Preferably, a CodeSandbox forked from https://codesandbox.io/s/github/marmelab/react-admin/tree/master/examples/simple
• A link to a GitHub repo with the minimal codebase to reproduce the issue

Other information:

Environment

React-admin version: “react-admin”: “^4.0.0-beta.1” Last version that did not exhibit the issue (if applicable): React version: “react”: “^17.0.2” Browser: Stack trace (in case of a JS error):