HubSpot: OAuth access token is not refreshed after expiration

What is the expected behaviour?

When the access token expires (every 30 minutes), the datasource should automatically use the stored refresh token to obtain a new access token.

What is the current behaviour?

After the access token expires, API requests fail with the following error:
{
"status": "error",
"statusCode": 401,
"statusMessage": "Unauthorized",
"message": "The OAuth token used to make this call expired 5 hour(s) ago.",
"category": "EXPIRED_AUTHENTICATION",
"correlationId": "019f601e-af3d-7912-b920-31130b6240c9"
}

How to reproduce the issue?

1. Configure a HubSpot datasource using OAuth.
2. Verify that API requests succeed.
3. Wait for the access token to expire (approximately 30 minutes), or use an expired access token.
4. Execute another query using the datasource.
5. Observe that the request fails with a 401 Unauthorized error instead of automatically refreshing the access token.

Screenshots or Screencast

Start by locating the HubSpot datasource's OAuth request and token handling, then reproduce the failure with an expired access token as described. Done means a subsequent API query automatically uses the stored refresh token to obtain a new access token and succeeds instead of returning a 401 error.