Properly configure Barrier between Trappist and Stout.

[hbulgarini]

We should configure accordingly the Barrier between Trappist and Stout so the fees are paid as expected.

For sub0 presentation i cut corners by adding the following configuration:

AllowUnpaidExecutionFrom<Base>

That basically allows that any execution coming from Base parachain just does not pay fees (of course it should not be like that).

[hbulgarini]

@stiiifff can i take this one?

[stiiifff]

@hbulgarini Sure. But we should properly describe the envisaged solution first. Can you update the issue description with what you have in mind ?

[stiiifff]

@hbulgarini Can you add a bit more info to this one so it can be moved to the Ready state ? thx !