A definition names no host path (ADR 0112); an adopted machine keeps its
data where the predecessor put it. Two settings, validated like endpoints:
places: {<directory id>: <path> | {path, owner}}
accesses: {<access id>: <path>}
An access may now be declared by id (`{"id": "series", "mode": "read-write"}`)
and named in mounts, env and content as ${access:<id>}; the assignment
says where it is on this node, and an access nobody placed is refused by
name. A definition still carrying a path keeps it as the default the
assignment replaces. A placed directory takes the assignment's owner
where it says one. Resolved in composition, so the host receives paths
and owners exactly as before.
jschoubben
17bbcc1596