Allow per-page user access control with `allowed-users` setting

[louis-thevenet]

Description

What problem would this feature solve?

I'd love to share my Glance instance with people but it has a private page.

It would be great if we could configure a list of allowed users for each page.

If applicable, what would the configuration for this feature look like?

pages:
  - name: Private
    allowed-users:
      - admin
      - friend
    columns: ...

[krillin666]

Would also love to see this implemented!

[beanaroo]

This would be great for hosting both personal and work dashboards on the same instance of glance.

[abhi-singhs]

I have created a PR https://github.com/glanceapp/glance/pull/858 that solves this. Please review and let me know.