squidclient: Drop cache_object protocol support (#1251)
Use `http` URL scheme for `mgr:command` cache manager requests instead.
Also fixed a bug: When `mgr:command` was used together with a `-w X`
command-line option, squidclient sent that proxy authentication password
`X` in the `cache_object` URL instead of sending the `Y` password from
the `-W Y` option (or no password at all if no `-W` option was given).
If no Authorization header had been sent, Squid's cachemgr_passwd
honored the `-w X` password sent in the cache_object URL. If
Authorization header had been sent, Squid's cachemgr_passwd honored the
corresponding `-W Y` password, ignoring any password sent in the
cache_object URL.
Now, squidclient uses Authorization HTTP header for sending cache
manager authentication credentials with `mgr:command` requests. Those
credentials are taken either from the `-U` and `-W` command-line options
(if `mgr:command` parameter lacks an embedded password) or from the `-U`
command line option and from the `mgr:command@password` parameter
(otherwise).
squidclient now sends Proxy authentication credentials if and only if
`-u` and `-w` command line options are given. These credentials may be
required to authenticate with the proxy, but they do not affect cache
manager authentication driven by the cachemgr_passwd directive.
Also prohibit specifying a command-line option with a password (`-w` or
`-W`) without specifying the corresponding user name (`-u` or `-U`).
Prior to this change, squidclient did not send the Proxy-Authorization
or Authorization header if the corresponding user name was missing but
did not complain about the problem.