Add missing Classroom CRUD Actions

[sean-dickinson]

What

• Currently classrooms can only be edited. We need to make it so that classrooms can also be created fresh and deleted

Context

• We weren't sure on what the pattern for these types of nested entities would be from a UI perspective so we skipped these actions and relied on the seeded data only.

Acceptance Critera

• Classrooms can be created in the UI
• Classrooms can be deleted in the UI
  • Students need to belong to a classroom, so we will need to consider how best to allow deletion of classrooms. The easiest for now would be to only deletion of empty classrooms (no students)

[hkakar5]

I've got the create half of this.