Chat data-model reform: - introduce on delete cascade on foreign key constraints so package can be removed easily e.g. from the subsite UI - remove remaining stored procedures (and function_args definitions) to relieve the burden on the development process and reduce divergency between oracle and postgres code - converge oracle and postgres datamodels: . oracle -> add missing messages_time_window column . postgres -> remove creation_date from chat_transcripts, which was found to be still existing on old downstream installations