Time-scheduled notifications impacted by rate-limiting

[mastercactapus]

Describe the Bug: The 15-minute rate-limiting feature implemented to prevent on-change spam and duplicate notifications is unintentionally applied to time-scheduled notifications, causing delays when multiple schedules are set to notify the same channel at the same time.

Expected Behavior: The 15-minute cooldown should only apply to on-change notifications and per-schedule. Time-scheduled notifications should be exempt from the rate-limiting (e.g., allowing 1 per second) to avoid unintended delays.

Observed Behavior: When multiple schedules are set up to notify the same channel at the same time, the 15-minute rate-limiting misapplied to time-scheduled notifications causes one of them to be delayed by 15 minutes.

Application Version: Affects the latest version up to the current master branch

Additional Context: This issue occurs within the schedule manager and not within the browser. There are no error messages or logs related to this issue, as the feature is working as "intended" in terms of rate-limiting but does not account for the case of having multiple schedules notify the same channel simultaneously and the potential necessity to distinguish application of the rate-limiting feature to different types of notifications.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity.

[hirenko-v]

same issue. We have a webhook attached to schedule on-call changes. When there are more than changes in a short period of time, the notification is delayed.