Redirect to error page when user is not allowed to represent party from cookie

### Description

Look at the error thrown in GetCurrentParty() in BootstrapGlobalService.cs, redirect appropriately.

### Additional Information

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### Tasks

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### Acceptance Criterias

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Start in BootstrapGlobalService.cs at GetCurrentParty() and trace how the thrown error is currently handled. Find the existing error-page redirect path and confirm what happens when the cookie represents a party the user cannot access; done means that case redirects to the appropriate error page.

Written by the indexing model from the issue text.