Add ToolCallMessage struct and update FunctionCallDetails to use dictionary for arguments

Author: Visual-Studio-Coder

Sources/Grok-API-SDK/Models/ChatData.swift

@@ -242,3 +242,11 @@ public struct SchemaProperty: Codable, Sendable {
     public let type: String
     public let description: String?
 }
+
+public struct ToolCallMessage: Codable, Sendable {
+    public let toolCalls: [ToolCall]?
+
+    enum CodingKeys: String, CodingKey {
+        case toolCalls = "tool_calls"
+    }
+}

Sources/Grok-API-SDK/Models/FunctionCall.swift

@@ -80,7 +80,13 @@ public struct ToolCall: Codable, Sendable {
 
 public struct FunctionCallDetails: Codable, Sendable {
     public let name: String
-    public let arguments: String
+    public let arguments: [String: String] // Change to dictionary to match JSON response
+
+    // Explicit public initializer
+    public init(name: String, arguments: [String: String]) {
+        self.name = name
+        self.arguments = arguments
+    }
 }
 
 public struct ToolCallResponse: Codable, Sendable {