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-45
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Content-Type: application/json
Expires: Sun, 21 Jul 2019 06:19:22 GMT
Vary: Accept

{
    "count": 43,
    "next": null,
    "previous": null,
    "results": [
        {
            "source": "direct-sharing-45",
            "name": "Nightscout Data Commons",
            "usernames": [
                "Sratty1",
                "nstanichevsky",
                "dylanleonard",
                "LongboatAline",
                "vanzaam",
                "DonutMaster",
                "Zii",
                "francesco",
                "dromore1911",
                "jamual90",
                "Tara1412",
                "gil",
                "jab12",
                "cascer1",
                "jwedding",
                "DIYdiabetes",
                "Sharingdata2012",
                "samihussein",
                "r_kingman",
                "Headrush1111",
                "pianoman2",
                "egal",
                "Unidragon",
                "dparsons",
                "woodduckie",
                "Deep_Forrest",
                "Ayeletssail",
                "wangm23456",
                "wbefield",
                "tapir314",
                "allisonm",
                "Martikkala",
                "246PWD",
                "AndyS",
                "whooze",
                "bmammon",
                "dustinjjohnson",
                "ibjopenaps",
                "craigio",
                "adhocz",
                "kretch",
                "jmo121402",
                "francescaneri",
                "protatoes",
                "cdmccook",
                "vishigondi",
                "MarcelZ",
                "loxam61",
                "WealOfFyre",
                "dramageek",
                "tal8645",
                "randomdiabetic",
                "thomasemge",
                "Justinvz",
                "mydata",
                "in10city",
                "biomesh",
                "pedrop",
                "vebaba",
                "Marc78400",
                "hasbend",
                "Dosefinder",
                "Sergio",
                "zreptil",
                "openaps000",
                "Unagimami",
                "PaperT1D",
                "sirfisch",
                "openaps17",
                "mike7985",
                "yeltsinxyz",
                "mhaeberli",
                "sethgagnon",
                "klaatu_gort",
                "gerarddwan",
                "silver_2000",
                "ecmihai"
            ]
        }
    ]
}