Add OpenStax to trusted book providers

[jimchamp]

Closes #6071

Adds OpenStax to our trusted book providers. This means that any read buttons for OpenStax books will direct patrons to the book's page on OpenStax.

Technical

Testing

1. Search for books with OpenStax as the publisher. Ensure that search results contain trusted provider read buttons.
2. Click on one of the read buttons. Ensure that the book's OpenStax details page is opened in a new tab.
3. Click the search results tab. Ensure that the toast message is present, and that its links work as expected.
4. Navigate to the book page of an OpenStax edition. Ensure that the trusted provider read button is present.
5. Ensure that the download options link works correctly.

Screenshot

OpenStax read button --- Book page

OpenStax read button and toast message --- Search results page

Stakeholders

@cdrini

[cdrini]

Nice! This looks great. Good sleuthing on finding all the pieces! I really need to DRY those up :P

Looking into OpenStax some more, it looks like the slug URLs aren't stable :( E.g. the first edition psychology textbook has slug psychology, but the url https://openstax.org/details/books/psychology redirects to psychology-2e. Looking at their docs, it looks like there is an ID inside their APIs:

E.g.

• Find ID number given slug: https://openstax.org/apps/cms/api/v2/pages/?slug=psychology
  • Here the slug is stable, though? It returns a different ID.
• Find url given ID number: https://openstax.org/apps/cms/api/v2/pages/45/

That's annoying :P But I guess the slug is stable; it's the URL that's redirecting. At some point in the future we might want to make a network request to get the metadata (e.g. https://openstax.org/apps/cms/api/v2/pages/45/ ) since that includes things like the direct read links as well. Added a note to the epic.