Fixes #369 — Fixes permission denied redirects

[oliverroick]

The following case leads to a redirect loop:

• The user is not authenticated.
• The user tries to access a page that requires authentication.
• The server redirects to the login page.
• The user authenticates themselves and is redirected to the original page.
• The user does have the required permissions on the original page and is redirected to the referrer, in this case the login page.
• Because the user is now authenticated, the login page again redirects to the original page. The redirect loop is entered.

This PR solves this issue by checking if the referrer is the login page and if a user is authenticated. The redirect as adapted based on the page the user tried to access:

• If the page is below the project dashboard level, the redirect points to the project dashboard.
• If the page is the project dashboard, the redirect points to the organisation dashboard.
• If the page is below the organisation dashboard level, the redirect points to the organisation dashboard.
• If the page is the organisation dashboard, the redirect points to the platform dashboard.

If the referrer is not the login page, the server will redirect to the referrer.