Add Domain project and shifted handlers to application.

wolverine/a-frame-architecture/FinancialApi.Domain/BalancedJournal.cs

@@ -0,0 +1,23 @@
+namespace FinancialApi.Domain;
+
+public record BalancedJournal
+{
+    public JournalEntry Entry { get; }
+
+    private BalancedJournal(JournalEntry entry) => Entry = entry;
+
+    public static BalancedJournal Create(Guid id, string description, DateTimeOffset createdAt, List<JournalLine> lines)
+    {
+        var debits = lines.Where(l => l.Type == EntryType.Debit).Sum(l => l.Amount);
+        var credits = lines.Where(l => l.Type == EntryType.Credit).Sum(l => l.Amount);
+
+        if (debits != credits)
+        {
+            throw new InvalidOperationException(
+                $"GAAP Violation: Total Debits ({debits}) must equal Total Credits ({credits})!"
+            );
+        }
+
+        return new(new JournalEntry(id, description, createdAt, lines));
+    }
+}