added concurrency handling 119

[Chansazm]

This helps when two users are trying to access the same resource at the same time, handles them gracefully.

[github-actions]

Formatting Issues Detected!

• Backend (Csharpier): Please run dotnet csharpier format . to fix formatting.

View Csharpier output

Error ./Project.App/Project.Api/Infrastructure/ConcurrencyExceptionFilter.cs - Was not formatted.
  The file did not end with a single newline.
Error ./Project.App/Project.Api/Infrastructure/ConcurrencyProblemDetails.cs - Was not formatted.
  The file did not end with a single newline.
Error ./Project.App/Project.Api/Repositories/UserRepository.cs - Was not formatted.
  ----------------------------- Expected: Around Line 52 -----------------------------
  
          // Update user balance
          public async Task UpdateBalanceAsync(User user)
  ----------------------------- Actual: Around Line 52 -----------------------------
  
          // Update user balance·
          public async Task UpdateBalanceAsync(User user)
  
Checked 75 files in 756ms.

[github-actions]

Formatting Issues Detected!

• Backend (Csharpier): Please run dotnet csharpier format . to fix formatting.

View Csharpier output

Error ./Project.App/Project.Api/Program.cs - Was not formatted.
  ----------------------------- Expected: Around Line 9 -----------------------------
  using Project.Api.Data;
  using Project.Api.Infrastructure;
  using Project.Api.Repositories;
  ----------------------------- Actual: Around Line 9 -----------------------------
  using Project.Api.Data;
  using Project.Api.Repositories;
  using Project.Api.Repositories.Interface;
  
Error ./Project.App/Project.Api/Infrastructure/ConcurrencyProblemDetails.cs - Was not formatted.
  The file did not end with a single newline.
Error ./Project.App/Project.Api/Infrastructure/ConcurrencyExceptionFilter.cs - Was not formatted.
  The file did not end with a single newline.
Error ./Project.App/Project.Api/Repositories/UserRepository.cs - Was not formatted.
  ----------------------------- Expected: Around Line 52 -----------------------------
  
          // Update user balance
          public async Task UpdateBalanceAsync(User user)
  ----------------------------- Actual: Around Line 52 -----------------------------
  
          // Update user balance·
          public async Task UpdateBalanceAsync(User user)
  
Checked 75 files in 760ms.