AO3-4059 Change chapters_controller to 404 if given work id is invalid

[Bilka2]

Issue

https://otwarchive.atlassian.net/browse/AO3-4059

Purpose

Changed the chapters controller so it 404s if the work id in the URL is invalid, instead of redirecting to the homepage.

Changed the chapters controller so it 404s if the chapter id in the URL is invalid and no work id is given.

References

PR Limit: 7 out of 5
Using reviewer bonus:
#4928
#5024

Credit

Bilka

[Bilka2]

Note for self, desired behavior, should be covered by tests:

1. /works/[existing] → goes to chapter or work as appropiate - happy path, used by many tests
2. /works/[existing]/chapters/[existing] → goes to chapter or work as appropiate - happy path, used by many tests
3. /works/[existing]/chapters/[nonexisting] → goes to chapter or work as appropiate -

   otwarchive/spec/controllers/chapters_controller_spec.rb

   Line 156 in 41d3878

   it "errors and redirects to work if chapter is not found" do

4. /works/[nonexisting] → 404 -

   otwarchive/spec/controllers/works/default_rails_actions_spec.rb

   Line 384 in 41d3878

   context "when work does not exist" do

5. /works/[nonexisting]/chapters/[existing] → 404 - test added here
6. /works/[nonexisting]/chapters/[nonexisting] → 404 - test added here
7. /chapters/[existing] → goes to chapter or work as appropiate - test added here
8. /chapters/[nonexisting] → 404 - test added here