Add a "mixed" type converter
|Priority:||Could have||Due date:|
"mixed" is used as a default type in case you don't explicitly provide proper type but there is no such converter, resulting in ambiguous behaviour.
When you create a command with a parameter in CommandController, and don't provide it's type properly by the @param annotation, "mixed" is determined as a default. When trying to use this command, you will get an Exception with message "Exception while property mapping at property path "":Could not find a suitable type converter for "mixed" because no such class or interface exists."
Create a "mixed" type converter that would be essentially NOP, thus making your code work the way you expect it to.