Replace host and port parameters with unified endpoint parameter for HTTP and MQTT connections

[Copilot]

This PR replaces separate host and port parameters with a single endpoint parameter for HTTP and MQTT connections, unifying the configuration approach with the Kafka connection feature introduced in issue #4666.

Changes Made

Core Structure Updates

• SenderThreadParams: Replaced separate ip and port fields with a unified endpoint field (format: "host:port")
• MQTT Functions: Updated sendMqttNotification() and getConnection() to accept endpoint parameter instead of separate host/port
• Notification Pipeline: Modified notification creation and consumption to use endpoint consistently

New Helper Functions

Added utility functions in src/lib/common/string.h:

• buildEndpoint(host, port) - Constructs endpoint string from host and port
• parseEndpoint(endpoint, host, port) - Parses endpoint string back to host and port with IPv6 support
• parseUrl(url, host, port, path, protocol, endpoint) - Overloaded version that extracts endpoint directly

Updated Flow

1. Creation: Notifier.cpp uses overloaded parseUrl() to extract endpoint directly from URL parsing
2. Storage: SenderThreadParams stores single endpoint string
3. Consumption: doNotify.cpp parses endpoint for HTTP calls or passes directly to MQTT

Benefits

• Unified Configuration: Consistent endpoint parameter across HTTP, MQTT, and Kafka
• Simplified Parameters: Single endpoint instead of separate host/port reduces complexity
• Reduced Errors: Less chance for host/port mismatch issues
• Optimized Flow: Endpoint extracted directly from URL parsing, no roundtrip through host/port
• Future-ready: Easier extension for additional protocols

Backward Compatibility

• HTTP httpRequestSend() function signature unchanged to minimize impact
• Existing URL parsing and notification logic continue to work
• No changes to external APIs or configuration files

Testing

• Added comprehensive unit tests for endpoint helper functions
• Added tests for new parseUrl overload with endpoint parameter
• Included edge cases, IPv6 support, and roundtrip validation
• Verified existing notification behavior remains unchanged

Fixes #4705.

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[fgalan]

@copilot I don't like this solution proposal too much...

Instead of

  paramsP->endpoint         = buildEndpoint(host, port);

The endpoint parameters should come set from the very beginning, instead of building if from port and host. In other words, host and port should not be needed at this point.

[Copilot]

@copilot I don't like this solution proposal too much...

Instead of
...

You're absolutely right! I've addressed this by adding an overloaded version of parseUrl() that extracts the endpoint directly during URL parsing, eliminating the need for the buildEndpoint(host, port) roundtrip.

The change ensures the endpoint parameter comes from the very beginning of the URL parsing process, so host and port are no longer needed at the point where we build the SenderThreadParams.

The commit 5111726 implements this optimization.