Slack notifier: Alert the team when an AP testing session begins

AP makes its testing calendar available via spreadsheet on its customer service site. More helpfully, it also appears to be available in the API.

Documentation: https://developer.ap.org/ap-elections-api/docs/index.html#t=Customer_Testing_Schedule.htm&rhsearch=test&rhhlterm=test&rhsyns=%20

Endpoint: https://api.ap.org/v3/reports/Calendar-CustomerTesting2024-Live?format=json

Sample:

            {
                "testDate": "2024-04-08",
                "testDay": "Monday",
                "eventAndSystemDate": "2024-04-23",
                "electionEvents": "PA Presidential/State Primary",
                "activity": "Customer Testing",
                "testTimeET": "4:30 pm-5:30 pm"
            },
...
            {
                "testDate": "2024-04-28",
                "testDay": "Sunday",
                "eventAndSystemDate": "2024-04-28",
                "electionEvents": "PR Dem Presidential Primary",
                "activity": "Election Day"
            },

(with thanks to @brentajones for the references)

It would be useful to have a notifier that:

Runs on an interval to check the API for the latest testing calendar
At the start time for each testing session, notify the team election slack channel. Example messages:
- AP: Customer Testing begins now — PA Presidential/State Primary (4:30pm-5:30pm)
- AP: Election Day — PR Dem Presidential Primary

For future-proofing, we should set up the notifier using the team visualsdev account rather than one person's individual account.

Related: #16

All work happening in the https://github.com/nprapps/elections-bots repo.

nprapps / elections24-primaries

Slack notifier: Alert the team when an AP testing session begins #165