Move models in separate projects

rag-api-models/DocumentClassification.cs

@@ -0,0 +1,10 @@
+namespace Rag.Models
+{
+    public sealed class DocumentClassification
+    {
+        public required string DocumentType { get; init; }
+        public double Confidence { get; init; }
+        public required string Title { get; init; }
+        public Dictionary<string, string> Metadata { get; init; } = new Dictionary<string, string>();
+    }
+}