[Enhancement] PPL Alerting: Optimize alert expiration logic to not always get full AlertV2 document

[toepkerd]

Is your feature request related to a problem?
Currently, Alert expiration logic fetches the full Alert document when searching for expired alerts. When alert v2 history is enabled, this is necessary to copy the alert over to the history index. However, when alert v2 history is disabled, only the alert ID and its monitor ID (for routing) is needed.

What solution would you like?
Increase the granularity of alert expiration logic to only retrieve alert ID and monitor ID of expired alerts when alert v2 history is disabled, as these are the only fields needed to hard delete an alert

[andrross]

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