exchanges/futures: Implement open interest (#1417)

* adds open interest to exchanges

* ADDS TESTING YEAH

* New endpoints, BTSE, RPCS, cached

* slight design change, begin gateio

You will need to get cached for
each exchange that supports it

* gateio, huobi, rpc

* fix up kraken, cache retrieval

* okx, gateio

* finalising all implementations and tests

* definitely my final ever commit on this

* Well, well, well

* final v2

* quick fix of bug

* test coverage, assert notempty, test helper

Added a new testhelper for currency
management because its very annoying
in a parallel test setting which wastes
so much space otherwise

* minimises REST requests for Open Interest

* types.Number merge misses

* Minimises Kraken REST calls

* len change, value -> pointer receiver

* further fixup

* fixes gateio, batch calculates open interest

* single gateio, lint const fixes

* rejig and more thorough oi for huobi

* formatting expansion

* minor fix for handling expiring contracts

* rm unused Binance strings

* add bybit support, fix bybit issues

* oopsie doopsie, dont look at my whoopsie

* Fix issue, remove feature

* move an irrelevant function for the pr

* mini bybit upgrades

* fixes cli request bug

gctrpc/rpc.proto

@@ -1501,6 +1501,27 @@ message GetOrderbookAmountByImpactResponse {
   bool full_orderbook_side_consumed = 11;
 }
 
+message GetOpenInterestRequest {
+  string exchange = 1;
+  repeated OpenInterestDataRequest data = 2;
+}
+
+message OpenInterestDataRequest {
+  string asset = 1;
+  CurrencyPair pair = 2;
+}
+
+message GetOpenInterestResponse {
+  repeated OpenInterestDataResponse data = 1;
+}
+
+message OpenInterestDataResponse {
+  string exchange = 1;
+  string asset = 2;
+  CurrencyPair pair = 3;
+  double open_interest = 4;
+}
+
 service GoCryptoTraderService {
   rpc GetInfo(GetInfoRequest) returns (GetInfoResponse) {
     option (google.api.http) = {get: "/v1/getinfo"};
@@ -2044,4 +2065,7 @@ service GoCryptoTraderService {
       body: "*"
     };
   }
+  rpc GetOpenInterest(GetOpenInterestRequest) returns (GetOpenInterestResponse) {
+    option (google.api.http) = {get: "/v1/getopeninterest"};
+  }
 }