Graceful service maintenance without nginx configuration (Part 1)

AccessBlock system was implemented at application level implemented because team lacked nginx access to block routing.

Access_block table stores path information contains path entries like /user/list.

Access_block_group table groups access_block entries group has a toggle that when true blocks all group's paths.

Front-end pages call a block-check REST API on each route, aPI compares current URL with access_block paths and returns true if matched.

Initial design did not implement API-level blocking type column was prepared but not used in this version.