Find MODE (string or list of strings) matching HOST and PORT.
DEPRECATED in favor of `auth-source-search'!
USERNAME is optional and will be used as "login" in a search
across the Secret Service API (see secrets.el) if the resulting
items don't have a username. This means that if you search for
username "joe" and it matches an item but the item doesn't have
a :user attribute, the username "joe" will be returned.
A non nil DELETE-EXISTING means deleting any matching password
entry in the respective sources. This is useful only when
CREATE-MISSING is non nil as well; the intended use case is to
remove wrong password entries.
If no matching entry is found, and CREATE-MISSING is non nil,
the password will be retrieved interactively, and it will be
stored in the password database which matches best (see `auth-sources'). MODE can be "login" or "password".