CP-12: Introduces limiter's currency conversion option (#44)

* CP-12: Introduces limiter's currency conversion option

* Changes new option flag to struct

* Fixes typo

* Adds missing field to create params

proto/limiter_config.thrift

@@ -26,6 +26,7 @@ struct LimitConfigParams {
  8: required LimitScope scope
  9: optional string description
  10: required OperationLimitBehaviour op_behaviour
+ 11: optional CurrencyConversion currency_conversion
 }
 
 struct LimitConfig {
@@ -40,11 +41,22 @@ struct LimitConfig {
  9: optional LimitScope scope
  10: optional string description
  12: optional OperationLimitBehaviour op_behaviour
+ /**
+ * Convert operation's amount if its context currency differs from
+ * limit-turnover metric (see `LimitTurnoverAmount`).
+ *
+ * If undefined and currency codes do not match, then limiter
+ * throws `InvalidOperationCurrency` exception (see
+ * limiter-proto).
+ */
+ 13: optional CurrencyConversion currency_conversion
 
  // deprecated
  4: optional LimitBodyType body_type_deprecated
 }
 
+struct CurrencyConversion {}
+
 struct OperationLimitBehaviour {
  1: optional OperationBehaviour invoice_payment_refund
 }