Class coaches can access class pages even when they are not assigned to the class

Observed behavior

~I can access the class groups rename form as coach but I have 403 error after I submit it.~

Class Coaches can access a classroom page even if they are not assigned to the classroom.

Expected behavior

~The class groups rename form most not accessible in coach.~

Pages from classrooms not assigned to the coach should not be accessible to the coach.

It should be redirected in the auth-message refer at the screenshot below

Steps to reproduce

• Log in as admin, then navigate at class groups page then copy the link.
• Log out as admin then Log in as coach then navigate at the class groups page using the link.
• Try to rename a class groups then submit it.

Context

Tell us about your environment, including:

• Kolibri 0.10.0.dev1.dev+git-33-g268dd8a
• macOS 10.13.3
• Chome Version 65.0.3325.181 (Official Build) (64-bit)

…

[rtibbles]

I think @ralphiee22’s solution is the right one, so that we can make role checks on the frontend more granular, but we should bump this to 0.12.

[jonboiser]

@ralphiee22 This came up when we were implementing class coaches. Should we change the permissions for Classrooms so not-assigned-to-this-class Coaches get a 40X error when going to these pages?