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-182
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Wed, 21 Aug 2019 02:39:31 GMT
Vary: Accept

{
    "count": 43,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-182",
            "name": "Google Location History Upload",
            "usernames": [
                "Clifford_G_Andrew_PGP84",
                "padams89",
                "gsdcomo",
                "gerwitz",
                "xeyve",
                "skram",
                "coolcole",
                "Damien",
                "wanderer",
                "gedankenstuecke",
                "benc",
                "jsbrava",
                "RemyWay",
                "Multicellular",
                "stephenbrad",
                "Tornado14",
                "OGolly",
                "filo",
                "ivanshim",
                "sso465",
                "fpacheco7",
                "jibe_b",
                "AigleDeTartare",
                "bubblbu",
                "HiImDannyGanz",
                "ajft",
                "dmaynard",
                "msantolini",
                "mako",
                "criniss",
                "aroldanf",
                "fury",
                "M_P",
                "reblaw",
                "Danspots",
                "nele80",
                "ChrisSampson87",
                "Masharako",
                "cdt",
                "geoffrothman",
                "carolinux",
                "senorcodecat",
                "oguzhanogreden",
                "paulusm",
                "cowninja",
                "yeltsinxyz",
                "Complutum",
                "devnull",
                "OH1702",
                "liubov",
                "fabianweiss",
                "dnkennedy",
                "CameoBlewett14",
                "cascrogg",
                "assimowitsch",
                "wip_abramson",
                "JakeB",
                "Zahar",
                "jeff9286",
                "jasteige",
                "ProtoRaptor92",
                "douglasgoodwin",
                "JKoskinen",
                "RyanRosenfeld",
                "rssfed23",
                "NickH"
            ]
        }
    ]
}