Add OpenFeedback endpoint

[FroMage]

The format should look like this:

{
    "sessions": {
        "2": {
            "speakers": [
                "lhwORZ2dSGbF1OG6VkfbjkOCzR12"
            ],
            "tags": [
                "Architecture & Paradigme"
            ],
            "title": "Entre industrialisation et artisanat, le métier de développeur",
            "id": "2",
            "startTime": "2019-06-27T16:20:00+02:00",
            "endTime": "2019-06-27T17:10:00+02:00",
            "trackTitle": "Amphi D"
        },
        "30": {
            "...": "",
            "hideInFeedback": true
        }
    },
    "speakers": {
        "lhwORZ2dSGbF1OG6VkfbjkOCzR12": {
            "name": "Olivier PONCET",
            "photoUrl": "https://avatars2.githubusercontent.com/u/29702924?v=4",
            "socials": [
                {
                    "name": "twitter",
                    "link": "https://twitter.com/ponceto91"
                }
            ],
            "id": "lhwORZ2dSGbF1OG6VkfbjkOCzR12"
        },
        "anotherId": {
            "...": ""
        }
    }
}

[FroMage]

Done by #6