Populate log tracking tables for Assignment, Course, and Role events

[Copilot]

The log tracking tables (AssignmentLog, CourseLog, RoleLog) were created but not being populated. This adds event logging at appropriate model lifecycle points.

Changes

Assignment events:

• CREATE on Assignment.new()
• DELETE on Assignment.remove()
• FORK on Assignment.fork()
• EDIT already logged in save_assignment() endpoint

Course events:

• CREATE on Course.new()
• DELETE on Course.remove()
• EDIT on Course.edit() - one log entry per field changed

Role events:

• GIVEN on User.add_role() and User.update_roles()
• REMOVED on Role.remove() and User.update_roles()
• CHANGED on Role.update_role()

Key additions:

• Added authorizer_id parameter to role operations to distinguish actor from subject (defaults to self-authorization)
• Updated course endpoints to pass current user as authorizer
• Optimized update_roles() to batch flush operations

# Example: Role logging with authorizer tracking
def add_role(self, name, course_id, authorizer_id=None):
    new_role = models.Role(name=name, user_id=self.id, course_id=course_id)
    db.session.add(new_role)
    db.session.commit()
    
    if authorizer_id is None:
        authorizer_id = self.id  # Self-authorization
    models.RoleLog.new(new_role.id, course_id, self.id, authorizer_id,
                       RoleLogEvent.GIVEN, name)
    return new_role

All logging follows existing SubmissionLog patterns with proper enum values and foreign key relationships.

Original prompt

We have created a set of new log tracking tables, but we are not currently populating them. We need to start logging events for these other tables.

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