Abstract a key/value pair, which has some RFC 2109 attributes.
Morsels are dictionary-like objects, whose set of keys is constant --
the valid RFC 2109 attributes, which are
The keys are case-insensitive.
The value of the cookie.
The encoded value of the cookie -- this is what should be sent.
The name of the cookie.
key, value, coded_value)
Set the key, value and coded_value members.
Whether K is a member of the set of keys of a Morsel.
Return a string representation of the Morsel, suitable
to be sent as an HTTP header. By default, all the attributes are included,
unless attrs is given, in which case it should be a list of attributes
to use. header is by default "Set-Cookie:".
The meaning for attrs is the same as in output().
Return a string representing the Morsel, without any surrounding HTTP