feat: add Plaid transaction handling and async queue processing

- introduced new migration to add Cursor column to AccountMetadata.
- updated AppDbContext model snapshot to reflect changes in the database schema.
- implemented async queue processing with ChannelAsyncQueue and AsyncQueueHostedService.
- created Plaid transaction handlers for added, modified, and removed transactions.
- developed PlaidTransactionService and PlaidTransactionSyncer for syncing transactions.
- added SyncUpdatesProcessor to handle sync updates from Plaid.
- updated tests to accommodate changes in institution and account metadata handling.

src/FiscalOS.Infra/Transactions/Plaid/PlaidModifiedTransactionHandler.cs

@@ -0,0 +1,75 @@
+using Account = FiscalOS.Core.Accounts.Account;
+using Transaction = FiscalOS.Core.Transactions.Transaction;
+
+namespace FiscalOS.Infra.Transactions.Plaid;
+
+internal interface IPlaidModifiedTransactionHandler
+{
+  void Handle(Account account, IEnumerable<Going.Plaid.Entity.Transaction> modified);
+}
+
+internal sealed class PlaidModifiedTransactionHandler : IPlaidModifiedTransactionHandler
+{
+  private readonly ILogger<PlaidModifiedTransactionHandler> _logger;
+  private readonly AppDbContext _appDbContext;
+
+  private PlaidModifiedTransactionHandler(
+    ILogger<PlaidModifiedTransactionHandler> logger,
+    AppDbContext appDbContext
+  )
+  {
+    _logger = logger;
+    _appDbContext = appDbContext;
+  }
+
+  public static PlaidModifiedTransactionHandler From(IServiceProvider serviceProvider)
+  {
+    return new(
+      serviceProvider.GetRequiredService<ILogger<PlaidModifiedTransactionHandler>>(),
+      serviceProvider.GetRequiredService<AppDbContext>()
+    );
+  }
+
+  public void Handle(Account account, IEnumerable<Going.Plaid.Entity.Transaction> modified)
+  {
+    var modifiedTransactionIds = modified.Select(t => t.TransactionId);
+    var existingModifiedTransactions = _appDbContext.Transactions
+      .Where(t => t.Metadata is PlaidTransactionMetadata && modifiedTransactionIds.Contains(((PlaidTransactionMetadata)t.Metadata).PlaidId))
+      .ToList();
+
+    foreach (var existing in existingModifiedTransactions)
+    {
+      if (existing.Metadata is not PlaidTransactionMetadata plaidMetadata)
+      {
+        _logger.LogWarning(
+          "Existing transaction {TransactionId} has non-Plaid metadata. Skipping update for this transaction.",
+          existing.Id
+        );
+        continue;
+      }
+
+      var plaidModifiedTransaction = modified.FirstOrDefault(t => t.TransactionId == plaidMetadata.PlaidId);
+
+      if (plaidModifiedTransaction is null)
+      {
+        _logger.LogWarning(
+          "No corresponding modified transaction found in Plaid response for existing transaction {TransactionId}. Skipping update for this transaction.",
+          existing.Id
+        );
+        continue;
+      }
+
+      var newTransactionData = Transaction.From(
+        existing.UserId,
+        existing.AccountId,
+        plaidModifiedTransaction.MerchantName,
+        plaidModifiedTransaction.OriginalDescription,
+        plaidModifiedTransaction.Amount,
+        plaidModifiedTransaction.Datetime,
+        plaidMetadata
+      );
+
+      _appDbContext.Entry(existing).CurrentValues.SetValues(newTransactionData);
+    }
+  }
+}