fix: outgoing QoS upgrade persistence

[kenkalang]

Proposed Changes

fix outgoing QoS and QoS upgrade persistence in maybe_offline_store.

Types of Changes

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• Bugfix (non-breaking change which fixes issue #XXXX)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
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• DevOps (Build scripts, pipelines...)