Add comprehensive collaborative editing documentation

[Copilot]

This PR adds complete documentation for the collaborative editing feature in Ibexa DXP v5.0+, resolving broken links in release notes and providing developers with comprehensive guides.

Overview

The collaborative editing feature allows multiple users to work together on content creation and editing through shared drafts, real-time editing, and invitation systems. This documentation provides everything needed to implement and customize the feature.

Documentation Added

Core User Guides

• Collaborative editing guide - Feature overview with key capabilities, use cases, and getting started instructions
• Installation guide - Complete setup with requirements, configuration options, and troubleshooting
• Usage guide - Detailed workflows for session management, invitations, and real-time collaboration
• Permissions guide - Comprehensive security configuration and access control

Developer Resources

• PHP API documentation - Complete API reference with services, value objects, and code examples
• Events documentation - Event system customization and integration patterns
• API events reference - Full event reference integrated into the API documentation section

Code Examples

• REST API controller with full CRUD operations for collaboration sessions
• Event subscriber with email notifications and logging
• Permission checking and validation examples

Integration

• Updated content management landing page to include collaborative editing
• Added complete navigation structure in mkdocs.yml
• Integrated collaboration events into API event reference
• Fixed broken links in release notes (v4.6 and v5.0)

Technical Details

The documentation covers the ibexa/collaboration package introduced in v5.0, including:

• Session management and participant handling
• Real-time synchronization with WebSocket support
• Invitation system for internal and external users
• Integration with existing permission system
• Event-driven architecture for customization

All documentation follows existing patterns and standards, with proper cross-references and validation. The build now passes with mkdocs build --strict without any warnings.

Testing

• ✅ MkDocs build passes without warnings
• ✅ All internal links validated
• ✅ Navigation properly integrated
• ✅ Code samples follow project standards

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• updates.ibexa.co
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/gNY53i /usr/bin/composer update (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Collaborative editing documentation</issue_title>
<issue_description>Prepare documentation for "Collaborative editing" feature.

Use data available in: https://github.com/ibexa/collaboration/</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #11

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