Make error pages for different authentication outcomes

[keiffer01]

Issue summary

Depending on certain outcomes, the user should be redirected to relevant error pages when they try to view a certain trip.

Expected behavior

When accessing the VIEW_ACTIVITIES page:

• if the user is a collaborator of the trip, they can view it as normal.
• if the tripId is not in Firestore, the user should be redirected to a page saying that the trip doesn't exist.
• if the user is not authenticated to view the trip, the user should be redirected to a page saying that they do not have permission to view the trip.

For the latter two cases, a button is also displayed that will redirect them back to the VIEW_TRIPS page.

Actual behavior

When accessing the VIEW_ACTIVITIES page:

• if the user is a collaborator of the trip, they can view it as normal.
• if the tripId is not in Firestore, a small error message is shown.
• if the user is not authenticated to view the trip, a small error message is shown.

The main difference between this and the expected behavior is that for the latter two cases, there is no option to go back to VIEW_TRIPS. They are stuck on the page.