HS 2.0R2: RADIUS server support to request Subscr Remediation

HS 2.0R2: RADIUS server support to request Subscr Remediation

The new hostapd.conf parameter subscr_remediation_url can be used to
define the URL of the Subscription Remediation Server that will be added
in a WFA VSA to Access-Accept message if the SQLite user database
indicates that the user need subscription remediation.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>