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-244
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Fri, 19 Aug 2022 01:52:08 GMT
Vary: Accept

{
    "count": 51,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-244",
            "name": "Mobility data of researchers",
            "usernames": [
                "wolfgang8741",
                "gedankenstuecke",
                "benc",
                "stephenbrad",
                "Olivier",
                "miqrom",
                "msantolini",
                "kaylea",
                "liubovv",
                "shivani",
                "Elly98",
                "AEIT",
                "tatianastoica",
                "raa",
                "npkk75",
                "Majean500",
                "Foo_me",
                "PutMeInAZoo"
            ]
        }
    ]
}