[DOI-3132] Get sources with subscribers count with mock data

[emoralesms]

Se crea endpoint que momentaneamente hasta que tengamos la estructura a consultar que nos devuelva la información desde la base devuelve data mock. Posteriormente se creara una tarea para reemplazar por una consulta. La respuesta actual es:

[
    {
        "source": "Manual",
        "amount": 12
    },
    {
        "source": "Importado",
        "amount": 340
    },
    {
        "source": "Formulario",
        "amount": 58
    },
    {
        "source": "MercadoShops",
        "amount": 1024
    },
    {
        "source": "RestAPI",
        "amount": 7
    },
    {
        "source": "TokkoBroker",
        "amount": 215
    },
    {
        "source": "Tiendanube",
        "amount": 100
    },
    {
        "source": "DataHub",
        "amount": 4321
    },
    {
        "source": "VTEX",
        "amount": 89
    },
    {
        "source": "Shopify",
        "amount": 15678
    },
    {
        "source": "Magento",
        "amount": 245
    },
    {
        "source": "Wordpress",
        "amount": 31
    },
    {
        "source": "Unbounce",
        "amount": 908
    },
    {
        "source": "PrestaShop",
        "amount": 67
    },
    {
        "source": "WooCommerce",
        "amount": 5400
    },
    {
        "source": "LearnPress",
        "amount": 14
    },
    {
        "source": "CRM2go",
        "amount": 2750
    },
    {
        "source": "Zoho",
        "amount": 620
    },
    {
        "source": "PieSync",
        "amount": 45
    },
    {
        "source": "Easycommerce",
        "amount": 1330
    },
    {
        "source": "ELAGestion",
        "amount": 26
    },
    {
        "source": "BMW RSP CRM",
        "amount": 9999
    },
    {
        "source": "MiTienda",
        "amount": 73
    },
    {
        "source": "TiendUp",
        "amount": 1840
    },
    {
        "source": "Jumpseller",
        "amount": 52
    },
    {
        "source": "Conversaciones",
        "amount": 410
    },
    {
        "source": "Landing Page",
        "amount": 3050
    },
    {
        "source": "Empretienda",
        "amount": 120
    },
    {
        "source": "OnSite",
        "amount": 8700
    },
    {
        "source": "TiendaNegocio",
        "amount": 5
    }
]

Checklist:

• I have paid attention to this PR title and description
• I have performed a self-review of my code
• I have built it locally (or my changes does not affect the build)
• I have checked all tests still run ok at Doppler.ReportingApiTest project
• I have added at least one simple unit test covering the new code