feat: Add cleanSession config, SDK v1.40.2 support, and Fedora build

[eduelias]

Motivation

This PR addresses MQTT connection reliability issues and adds support for the latest AWS IoT Device SDK C++ v2 (v1.40.2), along with improved build support for Fedora-based systems.

Background:

• Production systems experiencing DUPLICATE_CLIENT_ID errors during unclean service restarts
• AWS SDK v1.40.2 introduced breaking changes to socket API that prevented compilation of secure tunneling and sensor-publish features
• Need for configurable MQTT session behavior to support different reliability requirements
• Lack of official Fedora Docker build support

Issue number: N/A (proactive improvements)

Modifications

Change summary

1. Configurable Clean Session Flag

• Added clean-session boolean configuration option (defaults to true)
• Prevents DUPLICATE_CLIENT_ID errors by automatically disconnecting previous sessions
• Allows users to choose between session persistence (QoS 1+ message queuing) vs connection reliability
• Updated Config.h, Config.cpp, config-template.json, and documentation

2. AWS IoT Device SDK C++ v2 Update to v1.40.2

• Updated from commit 74c8b683 to 0d29d85a (v1.40.2)
• Fixed socket API compatibility in TcpForward.cpp and Socket.h to use new aws_socket_connect_options structure
• All features now compile successfully with latest SDK

3. Improved MQTT Disconnect Handling

• Enhanced SharedCrtResourceManager::disconnect() with forced cleanup on timeout
• Disables auto-reconnection during shutdown
• Adds 2-second grace period for broker propagation
• Better logging for disconnect states

4. Enhanced Systemd Service Configuration

• Increased TimeoutStopSec to 30 seconds for graceful MQTT disconnect
• Added restart loop prevention (max 5 restarts in 5 minutes)
• Proper signal handling with KillMode=mixed and SIGTERM → SIGKILL cascade
• Increased file descriptor limit to 65536

5. Fedora Build Support

• Added Fedora 42 Dockerfile following Amazon Linux pattern
• Builds OpenSSL 3.0.8 and CMake 3.24.4 from source for consistency
• Integrated with existing docker-build.sh script
• Multi-stage build for minimal runtime image

6. Additional Fixes

• Replaced vfork() with fork() in JobEngine.cpp (more portable, safer)
• Fixed dangling pointer in ConfigShadow.cpp
• Added .dockerignore for cleaner Docker builds
• Improved logging to show cleanSession value on connection

Revision diff summary

This is the initial submission.

Testing

Is your change tested? If not, please justify the reason.
✅ Yes, changes have been tested locally.

Please list your testing steps and test results.
WIP: Working on updating/fixing the tests now

1. macOS ARM64 Build Test

mkdir build && cd build
cmake ..
cmake --build . --target aws-iot-device-client