Add project files.

src/common/Elsa.Api.Common/Models/CountResponse.cs

@@ -0,0 +1,7 @@
+namespace Elsa.Models;
+
+/// <summary>
+/// Represents a count response that offers a unified format for returning count of things from API endpoints.
+/// </summary>
+/// <param name="Count">The number of items found for a given query.</param>
+public record CountResponse(long Count);