Add events/show endpoint to Calendar page

[not-so-smart]

GET /conversations/:group_id/events/show?event_id=0f15691677e444ceb64118bf39d41ec8

parameter is an event ID

response is just an Event object like everything else on that page

{
    "event": {
        "name": "Event Name",
        "description": "Event Description",
        "image_url": "https://i.groupme.com/1024x1024.png.8560aca484bf41f4863e2abec6016e07",
        "location": {
            "lat": 38.88949419381217,
            "lng": -77.0352490246296,
            "name": "Washington Monument",
            "address": "2 15th St NW (btwn Constitution Ave NW & Independence Ave SW) \nWashington, D.C. 20560 \nUnited States"
        },
        "start_at": "2021-08-30T01:00:00-04:00",
        "end_at": "2021-08-30T01:15:00-04:00",
        "is_all_day": false,
        "timezone": "America/New_York",
        "reminders": [
            0,
            604800
        ],
        "conversation_id": "70077952",
        "event_id": "0f15691677e444ceb64118bf39d41ec8",
        "creator_id": "74938777",
        "going": [
            "74938777"
        ],
        "not_going": [],
        "created_at": "2021-08-30T05:01:50Z",
        "updated_at": "2021-08-30T05:01:50Z"
    }
}