Added new callback types

src/errors.rs

@@ -5,3 +5,13 @@ pub struct NoUserInfo;
 #[derive(thiserror::Error, Debug)]
 #[error("Handler was already used")]
 pub struct HandlerUsed;
+
+#[derive(thiserror::Error, Debug)]
+pub enum InvalidCommand {
+    #[error("Invalid params")]
+    InvalidParams,
+    #[error("Not enough bytes in the name's hash")]
+    OutputTooShort,
+    #[error("Error decoding the values: {0}")]
+    NameDecodingError(#[from] base64::DecodeSliceError),
+}