Add a per-token "Allow querying user quota" switch. When it is on,
GET /api/usage/token/ also returns user_quota with the account's
remaining and used quota in quota units. New tokens start with the
switch on: the console form, POST /api/token/ without the field, and the
default token created at registration. Tokens created before this change
stay off. PUT /api/token/ keeps the stored value when the field is
absent, and the token audit lists the field when it changes.
The key usage and key log queries now check the key's IP whitelist the
same way API requests do, and answer 403 from an address outside it.
Expired and exhausted keys can still use both queries.
New API channels now query their balance from the upstream's
/api/usage/token/ with the channel key. When the upstream also returns
the owner's quota, the smaller of the key's and the owner's remaining
quota is the balance, and an unlimited key uses the owner's quota alone.
Without it, a limited key reports its own remaining quota, and an
unlimited key asks for the switch to be turned on upstream. Quota
converts to USD with the upstream's quota_per_unit from /api/status.
Refs #3122
Refs #6828
CaIon