Add more specs

[Valve]

Cover basic response parsing and various possible errors

[Valve]

@timur-rimsky
Here is the full response from the service that can be used to add specs:

http "https://geoip.maxmind.com/geoip/v2.1/city/45.17.22.11" 

HTTP/1.1 200 OK
Content-Length: 1476
Content-Type: application/vnd.maxmind.com-city+json; charset=UTF-8; version=2.1
Date: Thu, 04 Oct 2018 16:38:05 GMT
Server: geoip2-daemon

{
    "city": {
        "geoname_id": 4691930, 
        "names": {
            "de": "Fort Worth", 
            "en": "Fort Worth", 
            "es": "Fort Worth", 
            "fr": "Fort Worth", 
            "ja": "フォートワース", 
            "pt-BR": "Fort Worth", 
            "ru": "Форт-Уэрт", 
            "zh-CN": "沃思堡"
        }
    }, 
    "continent": {
        "code": "NA", 
        "geoname_id": 6255149, 
        "names": {
            "de": "Nordamerika", 
            "en": "North America", 
            "es": "Norteamérica", 
            "fr": "Amérique du Nord", 
            "ja": "北アメリカ", 
            "pt-BR": "América do Norte", 
            "ru": "Северная Америка", 
            "zh-CN": "北美洲"
        }
    }, 
    "country": {
        "geoname_id": 6252001, 
        "iso_code": "US", 
        "names": {
            "de": "USA", 
            "en": "United States", 
            "es": "Estados Unidos", 
            "fr": "États-Unis", 
            "ja": "アメリカ合衆国", 
            "pt-BR": "Estados Unidos", 
            "ru": "США", 
            "zh-CN": "美国"
        }
    }, 
    "location": {
        "accuracy_radius": 10, 
        "latitude": 32.8813, 
        "longitude": -97.3622, 
        "metro_code": 623, 
        "time_zone": "America/Chicago"
    }, 
    "maxmind": {
        "queries_remaining": 1498668
    }, 
    "postal": {
        "code": "76131"
    }, 
    "registered_country": {
        "geoname_id": 6252001, 
        "iso_code": "US", 
        "names": {
            "de": "USA", 
            "en": "United States", 
            "es": "Estados Unidos", 
            "fr": "États-Unis", 
            "ja": "アメリカ合衆国", 
            "pt-BR": "Estados Unidos", 
            "ru": "США", 
            "zh-CN": "美国"
        }
    }, 
    "subdivisions": [
        {
            "geoname_id": 4736286, 
            "iso_code": "TX", 
            "names": {
                "en": "Texas", 
                "es": "Texas", 
                "fr": "Texas", 
                "ja": "テキサス州", 
                "ru": "Техас", 
                "zh-CN": "德克萨斯州"
            }
        }
    ], 
    "traits": {
        "autonomous_system_number": 7018, 
        "autonomous_system_organization": "AT&T Services, Inc.", 
        "ip_address": "45.17.22.11", 
        "isp": "AT&T Internet Services", 
        "organization": "AT&T Internet Services"
    }
}