Add audit logs.

API/ROLAC.API/Services/MonthlyStatementService.cs

@@ -3,6 +3,8 @@ using Microsoft.EntityFrameworkCore;
 using ROLAC.API.Data;
 using ROLAC.API.DTOs.Expense;
 using ROLAC.API.Entities;
+using ROLAC.API.Entities.Logging;
+using ROLAC.API.Services.Logging;
 
 namespace ROLAC.API.Services;
 
@@ -10,7 +12,9 @@ public class MonthlyStatementService : IMonthlyStatementService
 {
     private readonly AppDbContext _db;
     private readonly IHttpContextAccessor _http;
-    public MonthlyStatementService(AppDbContext db, IHttpContextAccessor http) { _db = db; _http = http; }
+    private readonly IAuditLogger _audit;
+    public MonthlyStatementService(AppDbContext db, IHttpContextAccessor http, IAuditLogger audit)
+    { _db = db; _http = http; _audit = audit; }
 
     // See ExpenseService: the user id lives in the "sub" claim at runtime; NameIdentifier is for tests.
     private string CurrentUserId =>
@@ -66,6 +70,11 @@ public class MonthlyStatementService : IMonthlyStatementService
             ?? throw new KeyNotFoundException($"MonthlyStatement {id} not found.");
         s.IsFinalized = true; s.FinalizedAt = DateTimeOffset.UtcNow; s.FinalizedBy = CurrentUserId;
         await _db.SaveChangesAsync();
+
+        _audit.Write(
+            AuditActions.StatementFinalized, AuditCategories.Business, LogLevelEnum.Information,
+            entityName: nameof(MonthlyStatement), entityId: s.Id.ToString(),
+            summary: $"Monthly statement {s.Year}-{s.Month:D2} finalized");
     }
 
     private async Task RecomputeAsync(MonthlyStatement s)