feat: wip on login endpoint

- added basic REPR pattern
- added basic vert architecture
- implemented basica validation for single test case

src/FiscalOS.API/Login/Request.cs

@@ -0,0 +1,8 @@
+namespace FiscalOS.API.Login;
+
+public record LoginRequest(
+  [Required]
+  string Username,
+  [Required]
+  string Password
+);