Added support for MQTT notification mechanism

[pooja1pathak]

Proposed changes

A way to store data from mqtt queues. Fix for issue #609

Types of changes

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• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Maintenance (update of libraries or other dependences)

Checklist

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• [x] I have read the CONTRIBUTING doc
• [x] I have signed the CLA
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have run all the existing tests locally (not just those related to my feature) and there are no errors
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• [x] Any dependent changes have been merged and published in downstream modules

Further comments

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[github-actions[bot]]

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[pooja1pathak]

@c0c0n3 I am not sure about the test cases for this PR. If you have something in mind, then I can work to that.