trait to get exposure from external pallets such as staking

Signed-off-by: Uncle Stretch <uncle.stretch@ghostchain.io>

pallets/traits/src/exposure.rs

@@ -0,0 +1,7 @@
+use sp_runtime::traits::AtLeast32BitUnsigned;
+
+pub trait ExposureListener<Balance: AtLeast32BitUnsigned, EraIndex, AuthIndex> {
+    fn get_current_era() -> EraIndex;
+    fn get_total_exposure(era: EraIndex) -> Balance;
+    fn get_validator_exposure(index: AuthIndex) -> Balance;
+}

pallets/traits/src/lib.rs

@@ -1,3 +1,4 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 pub mod networks;
+pub mod exposure;