Добавил паттерн репозиторий

Payments/Payment.WebApi/Infrastructures/Databases/PaymentDbContext.cs

+using Microsoft.EntityFrameworkCore;
+using Payment.WebApi.Models.DbModels;
+
+namespace Payment.WebApi.Infrastructures.Databases;
+
+public class PaymentDbContext : DbContext
+{
+    public DbSet<User> Users { get; set; }
+    public DbSet<Supplier> Suppliers { get; set; }
+    
+    public PaymentDbContext(DbContextOptions<PaymentDbContext> options) : base(options)
+    {
+    }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+        
+        modelBuilder.SeedUser();
+        modelBuilder.SeedSupplier();
+        modelBuilder.SeedUserBalance();
+    }
+}
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Payments/Payment.WebApi/Models/DbModels/Supplier.cs

+namespace Payment.WebApi.Models.DbModels;
+
+public class Supplier
+{
+    public int Id { get; set; }
+    public string Name { get; set; }
+}
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Payments/Payment.WebApi/Models/DbModels/User.cs

+namespace Payment.WebApi.Models.DbModels;
+
+public class User
+{
+    public int Id { get; set; }
+    public string FirstName { get; set; }
+    public string LastName { get; set; }
+    public string? MiddleName { get; set; }
+    public int Age { get; set; }
+    public List<UserBalance> Balances { get; set; }
+
+    public User()
+    {
+        Balances = new List<UserBalance>();
+    }
+}
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Payments/Payment.WebApi/Models/DbModels/UserBalance.cs

+namespace Payment.WebApi.Models.DbModels;
+
+public class UserBalance
+{
+    public int Id { get; set; }
+    public decimal Amount { get; set; }
+    public string Currency { get; set; }
+    public int UserId { get; set; }
+    public User User { get; set; }
+}
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Payments/Payment.WebApi/Repositories/Interfaces/IRepository.cs

+namespace Payment.WebApi.Repositories.Interfaces;
+
+public interface IRepository<T>
+{
+    void Create(T item);
+    void Update(T item);
+    void Remove(T item);
+    void Save();
+}
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Payments/Payment.WebApi/Repositories/Interfaces/ISupplierRepository.cs

+using Payment.WebApi.Models.DbModels;
+
+namespace Payment.WebApi.Repositories.Interfaces;
+
+public interface ISupplierRepository : IRepository<Supplier>
+{
+    List<Supplier> GetAll();
+}
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Payments/Payment.WebApi/Repositories/Interfaces/IUserRepository.cs

+using Payment.WebApi.Models.DbModels;
+
+namespace Payment.WebApi.Repositories.Interfaces;
+
+public interface IUserRepository : IRepository<User>
+{
+    User? GetFirstOrDefaultById(int id);
+}
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Payments/Payment.WebApi/Repositories/SupplierRepository.cs

+using Payment.WebApi.Infrastructures.Databases;
+using Payment.WebApi.Models.DbModels;
+using Payment.WebApi.Repositories.Interfaces;
+
+namespace Payment.WebApi.Repositories;
+
+public class SupplierRepository : ISupplierRepository
+{
+    private readonly PaymentDbContext _context;
+
+    public SupplierRepository(PaymentDbContext context)
+    {
+        _context = context ?? throw new ArgumentNullException(nameof(context));
+    }
+
+    public List<Supplier> GetAll()
+    {
+        var suppliers = _context.Suppliers.ToList();
+        return suppliers;
+    }
+
+    public void Create(Supplier item)
+    {
+        _context.Suppliers.Add(item);
+    }
+
+    public void Update(Supplier item)
+    {
+        _context.Suppliers.Update(item);
+    }
+
+    public void Remove(Supplier item)
+    {
+        _context.Suppliers.Remove(item);
+    }
+
+    public void Save()
+    {
+        _context.SaveChanges();
+    }
+}
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Payments/Payment.WebApi/Repositories/UserRepository.cs

+using Payment.WebApi.Infrastructures.Databases;
+using Payment.WebApi.Models.DbModels;
+using Payment.WebApi.Repositories.Interfaces;
+
+namespace Payment.WebApi.Repositories;
+
+public class UserRepository : IUserRepository
+{
+    private readonly PaymentDbContext _context;
+
+    public UserRepository(PaymentDbContext context) =>
+        _context = context ?? throw new ArgumentNullException(nameof(context));
+
+    public User? GetFirstOrDefaultById(int id) => _context.Users.FirstOrDefault(s => s.Id == id);
+    public void Create(User item) => _context.Users.Add(item);
+    public void Update(User item) => _context.Users.Update(item);
+    public void Remove(User item) => _context.Users.Remove(item);
+    public void Save() => _context.SaveChanges();
+}
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