ладно ок

src/main/java/app/entities/other/SteamID.java

@@ -2,11 +2,13 @@ package app.entities.other;
 
 import app.exceptions.steam.InvalidSteamID;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
 
 @JsonSerialize
 public class SteamID {
     public String steam3;
     public String steam2;
+    @JsonSerialize(using = ToStringSerializer.class)
     public long steam64;
     public String community_url;