ruby: adding robot-name
ruby: robot-name: passing
ruby: grade-school: extracting a Roster class
fiddling with splitting apart Roster from School
elixir: sublist: off in the weeds again
ruby: grade-school: tests to identify access hole to roster
ruby: grade-school: WIP on extracting a Roster

which could be immutable when handed out by School
ruby: grade-school: protect school's roster

now it's somewhat immutable from the outside