added findByUserNameAsync to the interface and service

src/Application/Common/Interfaces/IIdentityService.cs

@@ -9,6 +9,7 @@ public interface IIdentityService
     Task<UserModel?> FindUserByIdAsync(string id);
     Task<UserModel?> GetCurrentUserAsync();
     Task<UserModel?> FindUserByEmailAsync(string id);
+    Task<UserModel?> GetUserByUserNameAsync(string userName);
     Task<bool> IsInRoleAsync(string userId, string role);
     Task<bool> AuthorizeAsync(string userId, string policyName);
     Task<Result> AddRoleAsync(string userId, string role);