Speed up access token cleanup with an index

crates/storage-pg/migrations/20260108175627_oauth_access_tokens_revoked_at_idx.sql

@@ -0,0 +1,9 @@
+-- no-transaction
+-- Copyright 2026 Element Creations Ltd.
+--
+-- SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+-- Please see LICENSE in the repository root for full details.
+
+-- This adds an index on the revoked_at field on oauth2_access_tokens to speed up cleaning them up
+CREATE INDEX CONCURRENTLY IF NOT EXISTS oauth_access_tokens_revoked_at_idx
+  ON oauth2_access_tokens (revoked_at) WHERE revoked_at IS NOT NULL;