Added tool calling support (#731)

Co-authored-by: krut_ni <nils.kruthoff@dlr.de>
Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Provider/OpenAI/ChatCompletionContent.cs

@@ -0,0 +1,41 @@
+using System.Text;
+using System.Text.Json;
+
+namespace AIStudio.Provider.OpenAI;
+
+internal static class ChatCompletionContent
+{
+    public static string? GetText(JsonElement? content)
+    {
+        if (content is not { } value)
+            return null;
+
+        if (value.ValueKind is JsonValueKind.String)
+            return value.GetString();
+
+        if (value.ValueKind is not JsonValueKind.Array)
+            return null;
+
+        var text = new StringBuilder();
+        foreach (var chunk in value.EnumerateArray())
+        {
+            if (chunk.ValueKind is JsonValueKind.String)
+            {
+                text.Append(chunk.GetString());
+                continue;
+            }
+
+            if (chunk.ValueKind is not JsonValueKind.Object ||
+                !chunk.TryGetProperty("type", out var type) ||
+                type.ValueKind is not JsonValueKind.String ||
+                !string.Equals(type.GetString(), "text", StringComparison.Ordinal) ||
+                !chunk.TryGetProperty("text", out var textElement) ||
+                textElement.ValueKind is not JsonValueKind.String)
+                continue;
+
+            text.Append(textElement.GetString());
+        }
+
+        return text.Length == 0 ? null : text.ToString();
+    }
+}