[derivatives] Adding limit order and stop order

[kimurayu45z]

enum ReservationType {
  UNKNOWN = 0;
  OVER_THRESHOLD = 1;
  UNDER_THRESHOLD = 2;
}

message MsgReserveOpenPosition {
  msg MsgOpenPosition = 1;
  ReservationType reservation_type = 2;
  string threshold_rate = 3; // sdk.Dec
}

message MsgReserveClosePosition {
  msg MsgClosePosition = 1;
  ReservationType reservation_type = 2;
  string threshold_rate = 3; // sdk.Dec
}

Architecture

• Just preserve reservations in DB when Msgs are executed
  • Sort reservations by threshold_rate for each market.
    • OverReservations
    • UnderReservations
• In every EndBlock handler, iterate sorted reservations.
  • If the oracle price crosses over the threshold_rate, execute the contained MsgOpenPosition or MsgClosePosition.