Project: Add 404 responses for projects and workflows

[eatyourgreens]

Check the project model for a project ID after the project API call resolves. If there's no project ID, set a 404 status code and show the default Next error page.

When there's a workflow ID in the URL, return 404 if it isn't listed in the project's active workflows.

Split data-fetching, and page props that only depend on the page URL, into a getStaticPageProps helper.

Package:
app-project

Closes #1694.

Review Checklist

General

• Are the tests passing locally and on Travis?
• Is the documentation up to date?

Components

• Has a storybook story been created or updated?
• Is the component accessible?
  • Can it be used with a screen reader? BBC guide to testing with VoiceOver
  • Can it be used from the keyboard? WebAIM guide to keyboard testing
  • Is it passing accessibility checks in the storybook?

Apps

• Does it work in all major browsers: Firefox, Chrome, Edge, Safari?
• Does it work on mobile?
• Can you yarn panic && yarn bootstrap or docker-compose up --build and app works as expected?

Publishing

• Is the changelog updated?
• Are the dependencies updated for apps and libraries that are using the newly published library?

Post-merging

• Did the app deploy to https://frontend.preview.zooniverse.org/projects/:project-name/:owner or https://frontend.preview.zooniverse.org/about?
• Is the new feature working or bug now fixed?
  • Is there a Talk or blog post written to announce the new feature(s)?
• Is the design working across browsers (Firefox, Chrome, Edge, Safari) and mobile?
  • Is this approved by our designer?
• Is this ready for production deployment?

[eatyourgreens]

I think this PR will 404 if Panoptes is down. Do we want to do that? The project model might need a bit of work to distinguish between API errors and successful requests for resources that don't exist.

[eatyourgreens]

The size of this PR jumped a lot today, but the increase is mostly tests. A lot of the SSR page props code has never had tests.

[srallen]

One minor style thing on the current generic 404 page:

We have an extra period in the message. This is a non-issue since I think implementing @beckyrother's designs would be the next iteration?

Nice set of new tests for this functionality with nock! Also, I since this partially implements what we discussed in #1997, it'd be nice to have the summary ADR of the decision written up to be able to reference while reviewing. Any chance you have time to write that up? Thanks!