feat: add curl() method to Request for generating cURL commands

This commit introduces a new `curl()` method in the `Request` class that generates a cURL command equivalent for the HTTP request. This is useful for debugging, logging, and reproducing requests outside of the application.

Key features:
- Includes HTTP method (`-X`), headers (`-H`), and request body (`--data`) if present.
- Handles escaping of special characters in body content.
- Appends the request URL.
- Provides KDoc consistent with the existing codebase.
- Added unit tests for:
  - GET requests with headers.
  - POST requests with complex JSON bodies containing nested objects and arrays.

Author: hamza-badar

okhttp/src/commonJvmAndroid/kotlin/okhttp3/Request.kt

@@ -423,4 +423,40 @@ class Request internal constructor(
 
     open fun build(): Request = Request(this)
   }
+  
+  /**
+   * Returns a cURL command equivalent to this request, useful for debugging and reproducing requests.
+   *
+   * This includes the HTTP method, headers, request body (if present), and URL.
+   *
+   * Example:
+   * ```
+   * curl -X POST -H "Authorization: Bearer token" --data "{\"key\":\"value\"}" "https://example.com/api"
+   * ```
+   *
+   * @return a cURL command string representing this request.
+   */
+  fun curl(): String {
+    val curl = StringBuilder("curl")
+    // Add method if not GET
+    if (method != "GET") {
+      curl.append(" -X ").append(method)
+    }
+    
+    for ((name, value) in headers) {
+      curl.append(" -H ")
+        .append("\"").append(name).append(": ").append(value).append("\"")
+    }
+    
+    body?.let { requestBody ->
+      val buffer = okio.Buffer()
+      requestBody.writeTo(buffer)
+      val bodyString = buffer.readUtf8()
+      curl.append(" --data ")
+        .append("\"").append(bodyString.replace("\"", "\\\"")).append("\"")
+    }
+    
+    curl.append(" \"").append(url).append("\"")
+    return curl.toString()
+  }
 }