EA Duplicate Detector - libreria per MetaTrader 5

Allow the EA to determine whether there are duplicate EAs on the chart based on conditions.

Expert.mqh comes from the library written by fxsaber at https://www.mql5.com/ru/code/19003.

enum ENUM_DUPLICATE_POLICY {
  POLICY_ALLOW_ALL,                    // Allow all (No detection)
  POLICY_ONE_PER_TERMINAL,             // Only one instance allowed globally in the terminal
  POLICY_ONE_PER_SYMBOL,               // Only one instance allowed per symbol (regardless of period)
  POLICY_ONE_PER_SYMBOL_PERIOD,        // Only one instance allowed per symbol and period
  POLICY_UNIQUE_PARAMS_ONLY            // Only allow running if parameters are different (regardless of symbol/period)
};