Add filter_body plugin for request/response body content filtering

[bryancall]

This plugin provides streaming body content inspection with configurable pattern matching and actions. It can be used to detect and mitigate CVE exploits and other malicious content patterns.

Features

• YAML-based configuration with rule definitions using filter/action schema
• Header-based filtering (AND logic between headers, OR within patterns)
• Case-insensitive header matching, case-sensitive body patterns
• Configurable actions per rule: log, block, add_header (with multiple headers)
• Support for both request and response body inspection
• Streaming transform with lookback buffer for cross-boundary patterns
• Optional max_content_length to skip large bodies
• Configurable HTTP methods (request) and status codes (response)
• Per-rule metrics counters for monitoring matches
• Support for <rule_name> substitution in header values

Actions

• log: Log pattern matches via TSError
• block: Set 403 Forbidden status and return error response
• add_header: Add custom headers to server request or client response

Includes

• Comprehensive RST documentation
• README.md quick reference
• ATSReplayTest autests for request/response filtering scenarios

Co-authored-by: Brian Neradt [email protected]