Refactor code structure for improved readability and maintainability; optimize performance in key functions.

src/Graph/StellaOps.Graph.Api/Services/IGraphLineageService.cs

@@ -0,0 +1,10 @@
+using System.Threading;
+using System.Threading.Tasks;
+using StellaOps.Graph.Api.Contracts;
+
+namespace StellaOps.Graph.Api.Services;
+
+public interface IGraphLineageService
+{
+    Task<GraphLineageResponse> GetLineageAsync(string tenant, GraphLineageRequest request, CancellationToken ct);
+}