fix: provide an explicit error for an invalid payload

also provide better tracing by setting the caused by error

Author: stakach

shard.yml

@@ -1,5 +1,5 @@
 name: jwt
-version: 1.3.0
+version: 1.3.1
 
 authors:
   - Potapov Sergey <blake131313@gmail.com>

src/jwt.cr

@@ -80,10 +80,12 @@ module JWT
     end
 
     {payload, header}
-  rescue Base64::Error
-    raise DecodeError.new("Invalid Base64")
-  rescue JSON::ParseException
-    raise DecodeError.new("Invalid JSON")
+  rescue error : Base64::Error
+    raise DecodeError.new("Invalid Base64", error)
+  rescue error : JSON::ParseException
+    raise DecodeError.new("Invalid JSON", error)
+  rescue error : TypeCastError
+    raise DecodeError.new("Invalid JWT payload", error)
   end
 
   def encode_header(algorithm : Algorithm, **keys) : String