Add rule-based filtering system with domain-specific controls

[abdullah-cognite]

Summary

This PR introduces a comprehensive rule-based filtering system that allows granular control over SSL inspection and content filtering on a per-domain basis.

Features

• Domain-specific SSL/TLS inspection (MITM) control with wildcard support (e.g., *.reddit.com)
• Per-domain content filtering by content-type or URL patterns
• Entire domain blocking - Set action to "block" with no URL patterns to block entire domain
• Rule priority system for conflict resolution
• Time-based and user-based rule restrictions
• Rules take precedence over global exception lists
• Full CRUD API for rule management with authentication
• Modern, collapsible UI for rule configuration
• Support for blocking specific content while allowing domain access

Technical Implementation

Backend

• Added Rule, RuleMatch, and related types in application/types/rule.go
• Implemented RuleManager with storage and matching logic in application/rules.go
• Created RESTful API endpoints for rule management in application/webserver/endpoints/handler_rules.go
• Integrated rule checking into proxy MITM decision flow in gatesentryproxy/proxy.go
• Added URL regex pattern matching for selective content blocking
• Added entire domain blocking by closing connection immediately when action=block
• Proper random ID generation using existing RandomString utility

Frontend

• Updated UI with rule creation, editing, and deletion capabilities
• Implemented collapsible rule view for better UX
• Added per-rule save functionality
• Action field always visible for easier configuration
• Default MITM action set to "enable" for new rules
• Enabled Rules menu item in navigation

Use Cases

1. Block Entire Domain: Set domain (e.g., video.twimg.com), MITM=enable, Action=block, no URL patterns
2. Selective HTTPS Inspection: Enable MITM only for specific domains (e.g., social media sites)
3. Content Blocking: Block specific content types (images, videos) or URL patterns on allowed domains
4. Reddit Example: Allow reddit.com but block the home feed (/svc/shreddit/feeds/home-feed)
5. Time-based Filtering: Apply rules only during specific time periods
6. User-specific Rules: Create rules that apply only to certain users

Testing

• Tested with reddit.com blocking specific feed URLs while allowing general browsing
• Tested entire domain blocking with video.twimg.com
• Verified rules take precedence over exception lists

Version

Updated to v1.18.0