fix: build and lots of obsolete warnings

modules/CombotAntiSpam/Combot/CombotApiResponse.cs

@@ -1,5 +1,5 @@
 using System;
-using Newtonsoft.Json;
+using System.Text.Json.Serialization;
 
 namespace Kruzya.TelegramBot.CombotAntiSpam.Combot;
 
@@ -7,24 +7,24 @@ internal class CombotApiResponse
 {
     public class ApiResult
     {
-        [JsonProperty("messages")]
+        [JsonPropertyName("messages")]
         public string[] Messages { get; set; }
             
-        [JsonProperty("time_added")]
+        [JsonPropertyName("time_added")]
         public int TimeAdded { get; set; }
             
-        [JsonProperty("offenses")]
+        [JsonPropertyName("offenses")]
         public int Offenses { get; set; }
 
         public DateTime AddedAt => DateTimeOffset.FromUnixTimeSeconds(TimeAdded).DateTime;
     }
 
-    [JsonProperty("ok")]
+    [JsonPropertyName("ok")]
     public bool IsSpammer { get; set; }
         
-    [JsonProperty("description")]
+    [JsonPropertyName("description")]
     public string Description { get; set; }
         
-    [JsonProperty("result")]
+    [JsonPropertyName("result")]
     public ApiResult Result { get; set; }
 }

modules/CombotAntiSpam/Combot/CombotClient.cs

@@ -22,6 +22,6 @@ public class CombotClient : ICombotClient
     public async Task<bool> IsSpammerAsync(User user)
     {
         var result = await _httpClient.GetJsonAsync<CombotApiResponse>($"?user_id={user.Id}");
-        return result.IsSpammer;
+        return result?.IsSpammer ?? false;
     }
 }