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-453
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Sun, 12 Jul 2020 18:13:14 GMT
Vary: Accept

{
    "count": 48,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-453",
            "name": "OH Data Port for Apple Health",
            "usernames": [
                "madprime",
                "jbedell",
                "padams89",
                "gsdcomo",
                "sprague",
                "gedankenstuecke",
                "scottleibrand",
                "onyame",
                "Iain",
                "devnull",
                "Jarvis532",
                "lbaldy",
                "Pojo",
                "HorayNarea",
                "m4p",
                "bst_b_well",
                "Laiudi",
                "UnstrungHero",
                "Craig997uk",
                "medimikka",
                "amcarlis",
                "volta1",
                "Iwynne",
                "Al70",
                "Clee",
                "glenlubbert",
                "rwmurphy",
                "Guillaume"
            ]
        }
    ]
}