Change Details

Part of [[ https://linear.app/comm/issue/ENG-4269/implement-the-database-schema | ENG-4269 ]]. Depends on D8443.

Part of [[ https://linear.app/comm/issue/ENG-4269/implement-the-database-schema | ENG-4269 ]]. Introduced a new `DatabaseClient` class to interface DDB. Depends on D8443.

Part of [[ https://linear.app/comm/issue/ENG-4269/implement-the-database-schema | ENG-4269 ]]. Introduced a new `DatabaseClient` class to interface DDB. Depends on D8443.