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-158
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Mon, 28 Sep 2020 04:30:19 GMT
Vary: Accept

{
    "count": 50,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-158",
            "name": "Open Humans Online Forums",
            "usernames": [
                "madprime",
                "beau",
                "jasonbobe",
                "Abe",
                "jtw",
                "gsdcomo",
                "emeadows317",
                "blackbearnh",
                "awz",
                "todrobbins",
                "wolfgang8741",
                "ArloJamesBarnes",
                "gedankenstuecke",
                "benc",
                "brianpardy",
                "eye144",
                "sarahwz",
                "Bouali",
                "stephenbrad",
                "genomenathan",
                "jrandymac",
                "Olivier",
                "danamlewis",
                "Agaricus",
                "miqrom",
                "saw2112",
                "Liang_Jiang",
                "dencook",
                "beckymagin",
                "mkbretsch",
                "Athina",
                "fresh_air",
                "arvkevi",
                "kdgreis",
                "mcescalante",
                "healthyageing",
                "GemmaKateRooney",
                "azuredominique",
                "apriha",
                "Crewest",
                "mdulaney",
                "M_P",
                "Tiina_S",
                "reblaw",
                "jcrben",
                "nobismRogierKoning",
                "DG",
                "S_liputra",
                "liubovv",
                "Nasianik",
                "agm929",
                "Sara",
                "Alleninv",
                "miguelrochefort",
                "Valeria",
                "davidpc",
                "Ckova",
                "bilal",
                "Gnisato",
                "TebbeUbben",
                "agnes",
                "SaraR",
                "febby2525",
                "testuser1"
            ]
        }
    ]
}