[PATCH 2/2] auth: Fix prefixing forward_fields without a value from client

[PATCH 2/2] auth: Fix prefixing forward_fields without a value from client

Bare tokens (without '=') were not prefixed, only key=value pairs were.
In practice this affected forward_fields, where a bare token such as
'nopassword' would land in extra_fields unprefixed instead of as
'forward_nopassword', allowing injection of internal auth control fields.

Gbp-Pq: Name 0002-auth-Fix-prefixing-forward_fields-without-a-value-fr.patch