Refactor. Add data layer

BudgetApp.Data/Entities/Salary.cs

@@ -0,0 +1,43 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace BudgetApp.Data.Entities;
+
+public class Salary
+{
+    public int Id { get; set; }
+
+    [Required, MaxLength(200)]
+    public string Name { get; set; } = string.Empty;
+
+    public decimal Amount { get; set; }
+
+    public RecurrenceType RecurrenceType { get; set; } = RecurrenceType.Monthly;
+
+    public DateTime StartDate { get; set; } = DateTime.Today;
+
+    public int AccountId { get; set; }
+    public Account Account { get; set; } = default!;
+
+    public int? CategoryId { get; set; }
+    public Category? Category { get; set; }
+
+    [Required]
+    public string UserId { get; set; } = string.Empty;
+    public ApplicationUser User { get; set; } = default!;
+
+    public string GetPaydaySummary() => RecurrenceType switch
+    {
+        RecurrenceType.Weekly  => $"Every week on {StartDate:dddd}",
+        RecurrenceType.Monthly => $"Monthly on the {GetOrdinal(StartDate.Day)}",
+        RecurrenceType.Yearly  => $"Annually on {StartDate:MMMM d}",
+        _                      => RecurrenceType.ToString()
+    };
+
+    private static string GetOrdinal(int day) => day switch
+    {
+        1 or 21 or 31 => $"{day}st",
+        2 or 22        => $"{day}nd",
+        3 or 23        => $"{day}rd",
+        _              => $"{day}th"
+    };
+}