IDL Gen annotations support

[christianlulaj]

IDL Gen is not able to generate IDL files that contain annotation such as @appendable. Modify idl gen to be able to handle annotations.

See list here of some common ones https://cyclonedds.io/content/guides/supported-idl.html

[jrebelo]

Adding annotations such as @appendable involves updating the way data is serialized and deserialized. This is certainly a feature we would like to have but is not high on the priority list at the moment so I can't say when it will be available.

As an alternative you could implement a custom serialize/deserialize for you types by re-implementing the traits defined in type support. It is not a really easy task though.