Move models in separate projects

rag-api-models/RagDocumentDetails.cs

@@ -0,0 +1,13 @@
+namespace Rag.Models
+{
+    public sealed class RagDocumentDetails
+    {
+        public required string Id { get; init; }
+        public required string DocumentType { get; init; }
+        public required string Title { get; init; }
+        public string? SourceUrl { get; init; }
+        public required string Text { get; init; }
+        public required string TextHash { get; init; }
+        public DateTimeOffset CreatedAt { get; init; }
+    }
+}