Refactor code and enhance API documentation

- Converted `Question.cs` and `Search.cs` records to `record class` syntax for clarity.
- Organized API endpoints with tags and added new GET and DELETE endpoints in `Program.cs`, including OpenAPI documentation improvements.
- Removed commented-out code in `Program.cs` for cleaner codebase.
- Introduced `WithTags` for better API operation categorization in Swagger UI.
- Added a TODO comment in `ChatService.cs` for future improvement on chunk length check.
- Clarified `using` directives in `VectorSearchService.cs` with namespace aliasing to improve readability.
- Refactored document deletion in `VectorSearchService.cs` to use a private helper method and expanded service capabilities with a new `GetDocumentsAsync` method.
- Introduced a new `Document` model in the `Models` namespace to support document fetching functionality.
- Simplified `appsettings.json` by removing `MaxTokens` configuration for `ChatCompletion` and `Embedding` services.

SqlDatabaseVectorSearch/Services/ChatService.cs

@@ -45,6 +45,7 @@ public class ChatService(IMemoryCache cache, IChatCompletionService chatCompleti
 
             """);
 
+        // TODO: Ensure that the chunks are not too long, according to the model max token.
         foreach (var result in chunks.Select(c => c.Content))
         {
             prompt.AppendLine(result);
@@ -75,7 +76,6 @@ public class ChatService(IMemoryCache cache, IChatCompletionService chatCompleti
         }
 
         cache.Set(conversationId, chat, appSettingsOptions.Value.MessageExpiration);
-
         return Task.CompletedTask;
     }
 }