@filename will be read in during the initialization of a
#SoupHSTSEnforcerDB, in order to create an initial set of HSTS
policies. If the file doesn't exist, a new database will be created
and initialized. Changes to the policies during the lifetime of a
#SoupHSTSEnforcerDB will be written to @filename when
#SoupHSTSEnforcer::changed is emitted.
Creates a #SoupHSTSEnforcerDB.
@filename will be read in during the initialization of a #SoupHSTSEnforcerDB, in order to create an initial set of HSTS policies. If the file doesn't exist, a new database will be created and initialized. Changes to the policies during the lifetime of a #SoupHSTSEnforcerDB will be written to @filename when #SoupHSTSEnforcer::changed is emitted.