Add /events endpoint to get events from Fellowship GCal

[shu8]

This PR adds a /events and /events/{id} endpoint to the amplify API, to get events from the Fellowship Google Calendar.

Note: it requires authentication, for now.

Fixes https://github.com/shu8/mlh-fellowship-0.2.1-halfway-hackathon/issues/6

Example event:

{
    "kind": "calendar#event",
    "etag": "\"3182278140440000\"",
    "id": "fcck4q8mdbv2a2a53omkaguhls",
    "status": "confirmed",
    "htmlLink": "https://www.google.com/calendar/event?eid=ZmNjazRxOG1kYnYyYTJhNTNvbWthZ3VobHMgbWFqb3JsZWFndWVoYWNraW5nLmNvbV9wcjNuampoNG9rMHBpOTNqZnFtNTFqZzJnMEBn",
    "created": "2020-06-02T12:01:27.000Z",
    "updated": "2020-06-02T23:04:30.220Z",
    "summary": "Arts and Crafts with Bob Ross",
    "description": "If you’d like to show off your creativity, join us for the <strong>Arts &amp; Crafts</strong> with Bob Ross!&nbsp;We’ll be watching a Bob Ross video together and then having a go at our own masterpieces, with an opportunity to share them at the end.",
    "location": "MLH Fellowship Discord (#mini-events)",
    "creator": {
        "email": "will.russell@majorleaguehacking.com"
    },
    "organizer": {
        "email": "majorleaguehacking.com_pr3njjh4ok0pi93jfqm51jg2g0@group.calendar.google.com",
        "displayName": "MLH Fellowship - Additional Fun & Educational Events",
        "self": true
    },
    "start": {
        "dateTime": "2020-06-03T09:00:00Z"
    },
    "end": {
        "dateTime": "2020-06-03T09:30:00Z"
    },
    "iCalUID": "fcck4q8mdbv2a2a53omkaguhls@google.com",
    "sequence": 1
}