[web] stop accepting the magic __message form parameter
This has been deprecated for a while, and replaced by _cwmsgid, which
doesn't allow arbitrary content.
for table, column in [
('transactions', 'tx_time'),
('tx_entity_actions', 'tx_uuid'),
('tx_relation_actions', 'tx_uuid')]:
repo.system_source.create_index(session, table, column)
commit()