Throw more meaningful exception when date format can't be determined

Author: CodeCasterNL

src/CodeCaster.GoodWe/GoodWeClient.cs

@@ -296,12 +296,20 @@ private async Task ReadUserDateFormatAsync()
             var dateSettingsResponse = await _client.PostAsync(endpoint, null);
             var responseObject = await dateSettingsResponse.Content.ReadFromJsonAsync<ResponseBase<DateFormatSettingsList>>();
 
-            var selected = responseObject.Data.DateFormats.FirstOrDefault(f => f.isselected);
-
-            _logger.LogDebug("Translating date format {selectedDateFormat}", selected.date_text);
-
-            var format = _dateFormats[selected.date_text];
+            if (responseObject == null || responseObject.HasError || responseObject.Data == null || responseObject.Data.Selected == null)
+            {
+                throw new InvalidOperationException("Could not determine date format for user");
+            }
+            
+            var formatId = responseObject.Data.Selected.date_text;
 
+            _logger.LogDebug("Translating date format {selectedDateFormat}", formatId);
+            
+            if (!_dateFormats.TryGetValue(formatId, out var format))
+            {
+                throw new ArgumentException("Could not translate date format " + formatId);
+            }
+            
             _serializerOptions = new JsonSerializerOptions
             {
                 PropertyNameCaseInsensitive = true,

src/CodeCaster.GoodWe/Json/GoodWeResponses.cs

@@ -58,15 +58,13 @@ public class LoginResponse
 
     public class DateFormatSettingsList
     {
-        [JsonPropertyName("list")]
-        public List<DateSetting> DateFormats { get; set; } = new();
+        public DateSetting? Selected { get; set; }
     }
 
     public class DateSetting
     {
         public string id { get; set; }
         public string date_text { get; set; }
-        public bool isselected { get; set; }
     }
 
     public class InverterData