COPDS-1489: remove old requests

[alex75]

In this PR:

• Added an entry point "remove-old-requests" to remove requests older than X days (default days=365)
• the entry points remove also requests-related events (this via a new delete-cascade db rule)
• the old records of adaptor_properties are removed too if they are without any child requests (using a new timestamp column)
• the PK request_id of system_requests is useless (and dangerous, it's an integer sequence instead of a biginteger), so it was removed, the new primary key is request_uid

[FussyDuck]

All committers have signed the CLA.