Refactor data layer, add business layer

DataLayer/scripts/crud/USP_DeleteUserAccount.sql

@@ -0,0 +1,23 @@
+
+CREATE OR ALTER PROCEDURE usp_DeleteUserAccount
+(
+    @UserAccountId UNIQUEIDENTIFIER
+)
+AS
+BEGIN
+    SET NOCOUNT ON
+    SET XACT_ABORT ON
+    BEGIN TRANSACTION
+
+    IF NOT EXISTS (SELECT 1 FROM UserAccount WHERE UserAccountId = @UserAccountId)
+    BEGIN
+        RAISERROR('UserAccount with the specified ID does not exist.', 16,
+        1);
+        ROLLBACK TRANSACTION
+        RETURN
+    END
+
+    DELETE FROM UserAccount 
+    WHERE UserAccountId = @UserAccountId;
+    COMMIT TRANSACTION
+END;