Post AHM disable of any to Relay xcm transactions

[TarikGul]

Summary

Post AHM it would be good to find out whether or not users can send funds to the relay chain. I think there are some edge cases where some accounts need some funds attached to them, but I am not sure if we should allow the construction of xcm messages to the relay chain, and or if we should just give a warning for chains that have the migration completed.

[andrew-ifrita]

@rockbmb and I discussed this briefly after the Westend AHM and he helped me investigate a bit.

Hm, I just tried:

1. sending exactly the (relay's) ED from Polkadot AH to Polkadot
2. sending above ED from PAH -> P
3. sending exactly the (relay's) ED from Westend AH to Westend
4. sending above the ED from WAH -> W

1 and 3 fail, as expected.
2 works, but 4 fails for the same reason as 1 and 3: xcmPallet.AssetsTrapped. This makes sense - with the AHM, we want to completely disallowed deposits on the relay.
Users see this, and can then proceed to rescue their trapped assets on the sending chain.

Anyway, I would say the conservative path is to officially deprecate sends to the relay with a warning once AH is out everywhere. After some time we can officially kill support and remove it entirely.

[andrew-ifrita]

This is actually a duplicate of #431 but I will close that issue instead as it is a bit dated and the author hasn't been active for some time.

[andrew-ifrita]

Marking as won't fix as we are dropping support for asset-transfer-api in favor of ParaSpell. See more in this issue: #652