one more fix in SetBusinessAccountUsername

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/requests/business_connection/SetBusinessAccountUsername.kt

@@ -25,6 +25,7 @@ data class SetBusinessAccountUsername(
     @SerialName(businessConnectionIdField)
     override val businessConnectionId: BusinessConnectionId,
     @SerialName(usernameField)
+    @Serializable(Username.Companion.WithoutAtSerializer::class)
     val username: Username
 ) : BusinessRequest.Simple<Boolean> {
     override fun method(): String = "setBusinessAccountUsername"
@@ -33,4 +34,4 @@ data class SetBusinessAccountUsername(
         get() = Boolean.serializer()
     override val requestSerializer: SerializationStrategy<*>
         get() = serializer()
-}
+}

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/types/ChatIdentifier.kt

@@ -7,6 +7,7 @@ import dev.inmo.tgbotapi.utils.RiskFeature
 import dev.inmo.tgbotapi.utils.internal.ClassCastsIncluded
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.builtins.serializer
 import kotlinx.serialization.descriptors.SerialDescriptor
 import kotlinx.serialization.encoding.Decoder
 import kotlinx.serialization.encoding.Encoder
@@ -148,6 +149,11 @@ value class Username (
     }
 
     companion object {
+        object WithoutAtSerializer : KSerializer<Username> {
+            override val descriptor: SerialDescriptor = String.serializer().descriptor
+            override fun deserialize(decoder: Decoder): Username = Username.prepare(decoder.decodeString())
+            override fun serialize(encoder: Encoder, value: Username) = encoder.encodeString(value.withoutAt)
+        }
         /**
          * Prepares a valid instance of [Username] by ensuring the given string starts with "@".
          *