Parses JSON without any __proto__ key, at every level.
`JSON.parse` keeps a `"__proto__"` key as an ordinary own key. Any later
`out[key] = value` copy of the result then sets `out`'s prototype to that
value, so the copy inherits fields that no walk over its own entries sees.
The config readers parse through this, so no copy of the config (the merge,
the secret split, the portal's masking) can meet the key. It sits beside
POLLUTING_KEY, the key it leaves out.
Parses JSON without any
__proto__key, at every level.`JSON.parse` keeps a `"__proto__"` key as an ordinary own key. Any later `out[key] = value` copy of the result then sets `out`'s prototype to that value, so the copy inherits fields that no walk over its own entries sees. The config readers parse through this, so no copy of the config (the merge, the secret split, the portal's masking) can meet the key. It sits beside POLLUTING_KEY, the key it leaves out.