Changes to Set retention policy

added the optional property cooldown_remaining_ms to the response with the 400 status

added the optional property cooldown_remaining_ms to the response with the 429 status

request property policy was restricted to a list of enum values

the request property max_age_hours became required

the request property policy became required

the max_age_hours request property's max was set to 43800.00

the max_age_hours request property's min was set to 24.00

added the new inactive-channels enum value to the request property policy

added the new old-messages enum value to the request property policy

endpoint added