future-private: add change margin mode request

src/LaravelBitunixApi.php

@@ -4,11 +4,12 @@ namespace Msr\LaravelBitunixApi;
 
 use GuzzleHttp\Client;
 use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+use Msr\LaravelBitunixApi\Requests\ChangeMarginModeRequestContract;
 use Msr\LaravelBitunixApi\Requests\FutureKLineRequestContract;
 use Msr\LaravelBitunixApi\Requests\Header;
 use Psr\Http\Message\ResponseInterface;
 
-class LaravelBitunixApi implements ChangeLeverageRequestContract, FutureKLineRequestContract
+class LaravelBitunixApi implements ChangeLeverageRequestContract, ChangeMarginModeRequestContract, FutureKLineRequestContract
 {
     private Client $publicFutureClient;
 
@@ -60,4 +61,19 @@ class LaravelBitunixApi implements ChangeLeverageRequestContract, FutureKLineReq
 
         return $response;
     }
+
+    public function changeMarginMode(string $symbol, string $marginCoin, string $marginMode): ResponseInterface
+    {
+        $body = [
+            'symbol' => $symbol,
+            'marginCoin' => $marginCoin,
+            'marginMode' => $marginMode,
+        ];
+
+        $response = $this->getPrivateFutureClient([], $body)->post('account/change_margin_mode', [
+            'json' => $body,
+        ]);
+
+        return $response;
+    }
 }

src/LaravelBitunixApiServiceProvider.php

@@ -4,6 +4,7 @@ namespace Msr\LaravelBitunixApi;
 
 use Msr\LaravelBitunixApi\Commands\LaravelBitunixApiCommand;
 use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+use Msr\LaravelBitunixApi\Requests\ChangeMarginModeRequestContract;
 use Msr\LaravelBitunixApi\Requests\FutureKLineRequestContract;
 use Spatie\LaravelPackageTools\Package;
 use Spatie\LaravelPackageTools\PackageServiceProvider;
@@ -31,5 +32,6 @@ class LaravelBitunixApiServiceProvider extends PackageServiceProvider
 
         $this->app->bind(FutureKLineRequestContract::class, LaravelBitunixApi::class);
         $this->app->bind(ChangeLeverageRequestContract::class, LaravelBitunixApi::class);
+        $this->app->bind(ChangeMarginModeRequestContract::class, LaravelBitunixApi::class);
     }
 }

src/Requests/ChangeMarginModeRequestContract.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Msr\LaravelBitunixApi\Requests;
+
+use Psr\Http\Message\ResponseInterface;
+
+interface ChangeMarginModeRequestContract
+{
+    /**
+     * Change margin mode for a trading pair
+     *
+     * @param string $symbol Trading pair (e.g., 'BTCUSDT')
+     * @param string $marginCoin Margin coin (e.g., 'USDT')
+     * @param string $marginMode Margin mode ('ISOLATION' or 'CROSS')
+     * @return ResponseInterface
+     */
+    public function changeMarginMode(string $symbol, string $marginCoin, string $marginMode): ResponseInterface;
+}