Add option for autojoining threads when opened

database/upgrades/09-more-thread-data.sql

@@ -0,0 +1,9 @@
+-- v9: Store more info for proper thread support
+ALTER TABLE thread ADD COLUMN creation_notice_mxid TEXT NOT NULL DEFAULT '';
+UPDATE message SET dc_thread_id='' WHERE dc_thread_id IS NULL;
+UPDATE reaction SET dc_thread_id='' WHERE dc_thread_id IS NULL;
+
+-- only: postgres for next 3 lines
+ALTER TABLE thread ALTER COLUMN creation_notice_mxid DROP DEFAULT;
+ALTER TABLE message ALTER COLUMN dc_thread_id SET NOT NULL;
+ALTER TABLE reaction ALTER COLUMN dc_thread_id SET NOT NULL;