feat: implement discussion mute/unmute feature with user and staff-level controls

[naincy128]

Description

This update introduces a comprehensive Mute / Unmute feature for discussion forums, enabling learners and staff to manage unwanted interactions more effectively while maintaining a healthy learning environment. The feature supports both personal and course-wide mute scopes, with clear role-based restrictions and overrides.

The implementation ensures muted content is hidden retroactively as well as for future posts, without notifying muted users. Special handling is included to prevent learners from muting staff or themselves, while giving staff full moderation control across the course.

Features

Learner Capabilities

• Added ability for learners to mute other learners (staff cannot be muted).
• Added personal mute list view and management.
• Enabled unmuting of previously muted users.
• Introduced “Mute and Report” action to mute a user and report their content in a single step.
• Prevented learners from muting themselves.

Staff Capabilities

• Includes all learner-level mute features.
• Added ability to mute users course-wide.
• Enabled viewing of both personal and course-wide mute lists.
• Allowed staff to unmute users across all mute scopes.

Key Behaviors

• Muted users are not notified when they are muted.
• Staff users cannot be muted by learners.
• Course-wide mutes override personal mutes.

Linked PRs

• Backend PR: edx/forum
• Frontend PR: edx/frontend-app-discussions