feat(api): add account workspaces and signed content events

server/src/WebDrop.Storage/SqliteAccountSigning.cs

@@ -0,0 +1,44 @@
+using Microsoft.Data.Sqlite;
+
+namespace WebDrop.Storage;
+
+public sealed record AccountDeviceSigningKey(string PublicKey, byte[] CertificateSignature);
+
+public sealed partial class SqliteAccountStore
+{
+    public AccountDeviceSigningKey? DeviceSigningKey(string username, string deviceId)
+    {
+        lock (_gate)
+        {
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = "SELECT public_key,certificate_signature FROM account_device_signing_keys WHERE username=$u AND device_id=$d";
+            cmd.Parameters.AddWithValue("$u", username); cmd.Parameters.AddWithValue("$d", deviceId);
+            using var reader = cmd.ExecuteReader();
+            return reader.Read() ? new(reader.GetString(0), (byte[])reader[1]) : null;
+        }
+    }
+
+    public bool SaveDeviceSigningKey(string username, string deviceId, string publicKey, byte[] signature)
+    {
+        lock (_gate)
+        {
+            using var device = _connection.CreateCommand();
+            device.CommandText = "SELECT 1 FROM account_devices WHERE username=$u AND id=$d";
+            device.Parameters.AddWithValue("$u", username); device.Parameters.AddWithValue("$d", deviceId);
+            if (device.ExecuteScalar() is null) return false;
+
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = """
+                INSERT INTO account_device_signing_keys(username,device_id,public_key,certificate_signature,modified_at)
+                VALUES($u,$d,$p,$s,$m)
+                ON CONFLICT(username,device_id) DO UPDATE SET public_key=excluded.public_key,
+                  certificate_signature=excluded.certificate_signature,modified_at=excluded.modified_at
+                """;
+            cmd.Parameters.AddWithValue("$u", username); cmd.Parameters.AddWithValue("$d", deviceId);
+            cmd.Parameters.AddWithValue("$p", publicKey); cmd.Parameters.AddWithValue("$s", signature);
+            cmd.Parameters.AddWithValue("$m", DateTimeOffset.UtcNow.ToUnixTimeMilliseconds());
+            return cmd.ExecuteNonQuery() == 1;
+        }
+    }
+
+}