Better error messages for "you're not allowed to see this project"

[rmunn]

Describe the bug
When tech support people get sent a link to the lexbox project and try to follow it, they are likely to run into a GraphQL error because they don't have permission to run the project page's GQL query. E.g. the one that Jason N just ran into:

We should consider making a slightly friendlier error message for this use case; this is not going to be the only time a tech support person tries to access a project they weren't a member of, so something like "You're not a member of this project" and then a redirect to their dashboard would at least be a little clearer.