Add HTTP/2 protocol support to dev proxy command

[Copilot]

Overview

This PR implements HTTP/2 protocol support for the dev proxy command, allowing developers to proxy HTTP/2 requests to backend servers.

Changes

Core Implementation

The proxy command now supports the --http2 flag to enable HTTP/2 protocol:

# Start an HTTP/2-enabled proxy server
$ dev proxy --port=12778 --target=12777 --http2

Key features:

• HTTP/2 Protocol Support: Uses Node.js native http2 module to create a secure HTTP/2 server
• Automatic SSL/TLS: HTTP/2 requires HTTPS, so SSL is automatically enabled (uses default certificates or custom ones via --ssl-cert and --ssl-key)
• HTTP/1.1 Fallback: Server supports both HTTP/2 and HTTP/1.1 clients through allowHTTP1: true option
• Header Filtering: Automatically filters connection-specific headers that are forbidden in HTTP/2 (connection, keep-alive, proxy-connection, transfer-encoding, upgrade)
• Backward Compatible: All existing proxy modes (HTTP, HTTPS) continue to work unchanged

Implementation Details

The HTTP/2 implementation handles requests differently from HTTP/1.1:

• Uses stream-based event handling for HTTP/2 requests
• Extracts HTTP/2 pseudo-headers (:method, :path, :authority)
• Converts headers to HTTP/1.1 format for backend communication
• Filters response headers to comply with HTTP/2 specifications
• Detects HTTP version to route HTTP/1.1 requests through the compatibility handler

Documentation

Updated README.md with:

• HTTP/2 usage examples
• Comprehensive parameter documentation
• Examples for all proxy modes

Testing

Verified functionality with:

• HTTP/2 client requests (using curl --http2)
• HTTP/1.1 fallback (using curl --http1.1)
• Regular HTTP and HTTPS proxy modes
• Request logging and error handling

Usage

# HTTP/2 proxy
$ dev proxy --port=12778 --target=12777 --http2

# HTTP/2 with custom certificates
$ dev proxy --http2 --ssl-cert=path/to/cert.pem --ssl-key=path/to/key.pem --target=https://api.example.com

# Traditional modes still work
$ dev proxy --ssl --target=12777
$ dev proxy --target=https://www.example.com

Closes the issue requesting HTTP/2 support for the dev proxy command.

Original prompt

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This section details on the original issue you should resolve

<issue_title>dev proxy support http2</issue_title>
<issue_description>
when the dev proxy command is execued with --http2 parameter, it initiate a ssl and http2-enabled server to act as a proxy that relays request to the backend</issue_description>

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

Fixes #57

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