Add resources section to teacher-facing lesson plan

[bethanyaconnor]

Adds resources to the lesson front page.

The "audience" field changed a bit from CB, where it was a checkbox indicating whether it was a teacher resource or not.

• Currently, the audience field isn't required (though maybe we should think about requiring that), so I added a catch-all "All" bucket for now.
• In addition, there is an option for "Verified Teacher". I added some logic on the backend to only display those resources if the current user is an authorized_teacher.

Authorized teacher:

Signed out user:

Links

• jira

Testing story

manual testing and unit tests

Reviewer Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[davidsbailey]

Great work, Bethany!