[RAM] Create data model for scheduled and recurring snoozes

[Zacqary]

Modify SavedObject specification to include more than just a snoozeEndTime but also:

• Scheduled snooze at a specific future time (this can be multiple scheduled snoozes)
• Recurring snooze on every day of a week (e.g. Saturday, Sunday)
• Recurring snooze every interval (e.g. 1M, 2w)

Also create a migration to move from the old data model (Just snoozeEndTime) to this new model

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)

[Zacqary]

Turns out this already touches a lot of existing functionality. The data model I'm migrating to is:

      "snoozeIndefinitely": {
        "type": "boolean"
      },
      "snoozeSchedule": {
        "properties": {
          "id": {
            "type": "keyword"
          },
          "startTime": {
            "type": "date",
            "format": "strict_date_time"
          },
          "duration": {
            "type": "long"
          },
          "repeatInterval": {
            "type": "keyword"
          },
          "occurrences": {
            "type": "long"
          },
          "repeatEndTime": {
            "type": "date",
            "format": "strict_date_time"
          }
        }
      }

snoozeSchedule takes the form of an array of these props, of which only startTime and duration are required. Using these two props, we can replicate the functionality of the existing snoozeEndTime. But there's a lot of different functions expecting a single end date string, so I've got a lot to untangle even just for a data migration.

When we add the scheduled snooze UI, we'll also make use of:

• repeatInterval: Takes the form of a time interval like 1d, 3w, or a day of week string, e.g. DOW:06 to snooze every Saturday and Sunday. (Using Date.prototype.getDay() output of 0-6 for Sunday through Saturday)
• occurrences: An optional number of occurrences to repeat the snooze for
• repeatEndTime: An optional date to keep snoozing until
• id: Each scheduled snooze will be assigned one of these so that we can target it with an unsnooze if the user wants to cancel it

Because this is an array that can store an indefinite number of scheduled snoozes, we may want to create a cleanup task to clear expired snoozes from the snoozeSchedule.

[Zacqary]

After discussing with @XavierM and @pmuellr, we're simplifying the data model in favor of setting an iCal RRULE for any recurring snoozes.

[pmuellr]

This sounds great. Love aligning on standards, so we can say "we didn't invent this, it's a 'standard'" :-)

Opens the door to us being able to "import/export" some of this calendar-ish data with other apps. I did take a look at some other incident providers, and they don't seem to have great support for this kind of thing, but ... I'll bet some do. Could be an interesting integration angle.

Kinda funny, when I click on the link in the comment ^^^, I get the following: