Creates an alert from the given command, attempts delivery, and persists state.
Applies spam mitigation: If an unread alert for the same threshold exists and was created within the last hour, creation is skipped.
The data required to create the alert.
The created alert identifier, or null if suppressed.
Retrieves an alert by its string identifier.
The string identifier of the alert.
The Alert instance when found.
Coordinates alert creation, delivery, and repository operations.
Param: repository
The persistence implementation for alerts.
Param: sender
The transport responsible for sending alerts.