Configuration: Skip thread containment by default

In my tests the interaction between thread containment and other restrictions
makes postgresql create some very bad query plans. This caused direct messages
to time out on soykaf, for example.

CHANGELOG.md

@@ -56,6 +56,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 - **Breaking:** Configuration: move from Pleroma.Mailer to Pleroma.Emails.Mailer
+- Thread containment / test for complete visibility will be skipped by default.
 - Enforcement of OAuth scopes
 - Add multiple use/time expiring invite token
 - Restyled OAuth pages to fit with Pleroma's default theme

config/config.exs

@@ -244,7 +244,7 @@ config :pleroma, :instance,
   safe_dm_mentions: false,
   healthcheck: false,
   remote_post_retention_days: 90,
-  skip_thread_containment: false,
+  skip_thread_containment: true,
   limit_unauthenticated_to_local_content: true
 
 config :pleroma, :app_account_creation, enabled: true, max_requests: 25, interval: 1800