Add era to Unbonded event (#11770)

* Add era to `Unbonded` event

fixes #11749

* Fix missing tests

* Add comment for `era` field in `Unbonded` struct.

Co-authored-by: parity-processbot <>

substrate/frame/nomination-pools/src/lib.rs

@@ -1349,7 +1349,7 @@ pub mod pallet {
 		///   pool.
 		/// - `points` is the number of points that are issued as a result of `balance` being
 		/// dissolved into the corresponding unbonding pool.
-		///
+		/// - `era` is the era in which the balance will be unbonded.
 		/// In the absence of slashing, these values will match. In the presence of slashing, the
 		/// number of points that are issued in the unbonding pool will be less than the amount
 		/// requested to be unbonded.
@@ -1358,6 +1358,7 @@ pub mod pallet {
 			pool_id: PoolId,
 			balance: BalanceOf<T>,
 			points: BalanceOf<T>,
+			era: EraIndex,
 		},
 		/// A member has withdrawn from their pool.
 		///
@@ -1683,6 +1684,7 @@ pub mod pallet {
 				pool_id: member.pool_id,
 				points: points_unbonded,
 				balance: unbonding_balance,
+				era: unbond_era,
 			});
 
 			// Now that we know everything has worked write the items to storage.