Asset Conversion: Pool Touch Call (#3251)

Introduce `touch` call designed to address operational prerequisites
before providing liquidity to a pool.

This function ensures that essential requirements, such as the presence
of the pool's accounts, are fulfilled. It is particularly beneficial in
scenarios where a pool creator removes the pool's accounts without
providing liquidity.

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Co-authored-by: command-bot <>

substrate/frame/assets/src/lib.rs

@@ -1697,7 +1697,9 @@ pub mod pallet {
 
 		fn should_touch(asset: T::AssetId, who: &T::AccountId) -> bool {
 			match Asset::<T, I>::get(&asset) {
+				// refer to the [`Self::new_account`] function for more details.
 				Some(info) if info.is_sufficient => false,
+				Some(_) if frame_system::Pallet::<T>::can_accrue_consumers(who, 2) => false,
 				Some(_) => !Account::<T, I>::contains_key(asset, who),
 				_ => true,
 			}