Fetch one row by primary key for the ops read plane.

The list endpoints answer what exists; a console that renders a list then needs the row behind a click, and until now nothing in the plane could serve one - there was no /ops/players/:id and no /ops/matches/:id anywhere.

The id is checked for uuid shape before it reaches the database (asobi_ops_params:uuid/1) and the row is passed through the endpoint's own projection on the way out, so a lookup can never return a field its list would have withheld.