Return an array where each entry is an object with this form:

{ source: "fitbit", name: "Fitbit", usernames: ["beau", "madprime"] }

GET /api/public-data/members-by-source/?source=direct-sharing-178
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Mon, 18 Oct 2021 17:42:58 GMT
Vary: Accept

{
    "count": 53,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-178",
            "name": "QCycle",
            "usernames": [
                "saw2112",
                "cotton",
                "JeniferLynnGarrett",
                "IonutMurariu",
                "jyork",
                "mlukaczyk",
                "Athina",
                "gedankenstuecke",
                "josiegrant",
                "weboesel",
                "hagarrett",
                "S_IllerDrachman",
                "phenylalanine",
                "jsuew",
                "teresaeg",
                "bsoule",
                "maggied",
                "soundinspace",
                "musecycles",
                "sarablenk",
                "kwilst",
                "YA",
                "mara",
                "azuredominique",
                "aaaabee",
                "Mspantherina"
            ]
        }
    ]
}