How to define a new file extension for the Entity Designer

Hi,

I want to use "Model1.foo" as the file instead of "Model1.edmx" so that I can use IModelConversionExtension extensibility.
I think this requires me to register the ".foo" extension in the Registry so the EF Designer knows to open such type of file.
And I think I need to create a .pkgdef for these registry entries.

Please can you give me an example.

I would need to know the GUID for the EF Designer so it knows the file extension is associated.
And whether my new .foo file needs to support the .diagram as an associated type.

Thanks

John