feat: add TLS support for MQTT datastore (#340)

[HrishikeshUchake]

• Added TLS configuration to MQTT producer
• Updated config loader to support MQTT TLS fields
• Added unit tests for MQTT TLS configuration
• Updated README and examples with MQTT TLS configuration example

Description

I have implemented the fix for issue [#340], which requested support and examples for connecting to an MQTT broker over SSL/TLS (e.g., port 8883).

Summary of Changes

1. MQTT Datastore Enhancements
   TLS Configuration: Added a TLSConfig struct to the MQTT [Config] in [mqtt.go] to support enabled and ca (path to CA certificate) fields.
   TLS Implementation: Updated [NewProducer] in [mqtt.go] to initialize a [tls.Config] when enabled. It now correctly loads the CA certificate from the specified path and applies it to the Paho MQTT client options.
2. Configuration & Validation
   Config Loading: Updated the configuration initialization tests in [config_initializer_test.go] and [test_configs_test.go] to ensure the new MQTT TLS fields are correctly parsed from JSON.
   Unit Testing: Added comprehensive tests in [mqtt_test.go] to verify that TLS is correctly configured when enabled and that CA certificates are properly loaded.
3. Documentation & Examples
   Example Config: Updated [server_config.json] with a complete MQTT over SSL configuration example.
   README Update: Added the new MQTT TLS configuration parameters to the [README.md] documentation

Fixes #340

Type of change

Please select all options that apply to this change:

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bug fix (non-breaking change which fixes an issue)
• Documentation update

Checklist:

Confirm you have completed the following steps:

• My code follows the style of this project.
• I have performed a self-review of my code.
• I have made corresponding updates to the documentation.
• I have added/updated unit tests to cover my changes.
• I have added/updated integration tests to cover my changes.

[HrishikeshUchake]

Hi @patrickdemers6, @agbpatro, could you please review this? I'd love to hear your opinions and suggestions on this. Thank you so much!