feat(account): add deletion lifecycle

JobTrackerApi/Services/AccountDeletionTombstoneStore.cs

@@ -0,0 +1,64 @@
+using System.Text.Json;
+
+namespace JobTrackerApi.Services;
+
+public sealed record AccountDeletionTombstone(string SchemaVersion, Guid RequestId, string OwnerKey, DateTimeOffset CompletedAtUtc);
+
+public sealed class AccountDeletionTombstoneStore(AppPaths paths)
+{
+    private const string SchemaVersion = "jobtracker.account-deletion-tombstone.v1";
+    private readonly SemaphoreSlim _gate = new(1, 1);
+    private string LedgerPath => Path.Combine(paths.AccountDeletionTombstonesRoot, "tombstones.jsonl");
+
+    public async Task AppendAsync(Guid requestId, string ownerKey, DateTimeOffset completedAtUtc, CancellationToken cancellationToken)
+    {
+        await _gate.WaitAsync(cancellationToken);
+        try
+        {
+            var existing = await ReadUnsafeAsync(cancellationToken);
+            if (existing.Any(item => item.RequestId == requestId)) return;
+            Directory.CreateDirectory(paths.AccountDeletionTombstonesRoot);
+            var line = JsonSerializer.Serialize(new AccountDeletionTombstone(SchemaVersion, requestId, ownerKey, completedAtUtc));
+            await File.AppendAllTextAsync(LedgerPath, line + Environment.NewLine, cancellationToken);
+        }
+        finally
+        {
+            _gate.Release();
+        }
+    }
+
+    public async Task<IReadOnlyList<AccountDeletionTombstone>> ReadAsync(CancellationToken cancellationToken)
+    {
+        await _gate.WaitAsync(cancellationToken);
+        try { return await ReadUnsafeAsync(cancellationToken); }
+        finally { _gate.Release(); }
+    }
+
+    private async Task<IReadOnlyList<AccountDeletionTombstone>> ReadUnsafeAsync(CancellationToken cancellationToken)
+    {
+        if (!File.Exists(LedgerPath)) return Array.Empty<AccountDeletionTombstone>();
+        var result = new List<AccountDeletionTombstone>();
+        foreach (var line in await File.ReadAllLinesAsync(LedgerPath, cancellationToken))
+        {
+            if (string.IsNullOrWhiteSpace(line)) continue;
+            try
+            {
+                var item = JsonSerializer.Deserialize<AccountDeletionTombstone>(line);
+                if (item is null
+                    || item.SchemaVersion != SchemaVersion
+                    || item.RequestId == Guid.Empty
+                    || item.OwnerKey.Length != 64
+                    || item.OwnerKey.Any(character => !Uri.IsHexDigit(character)))
+                    throw new InvalidOperationException("The account-deletion tombstone ledger contains an invalid record.");
+                result.Add(item);
+            }
+            catch (JsonException)
+            {
+                // A partial/corrupt line is never ignored by replay callers: expose a sentinel so
+                // startup fails closed instead of declaring the tombstone set complete.
+                throw new InvalidOperationException("The account-deletion tombstone ledger contains an invalid record.");
+            }
+        }
+        return result;
+    }
+}