[Webpush] Alternate/fallback mechanism for receiving

[Costin Manolache <[e-mail]>]

Hi,

I know this may be a bit controversial, and I love both HTTP/2 and push
promises :-)

However, to make it easier to implement/test/deploy, would it be possible
to add a small
change to sections 7, 7.1 and 7.3:

'if http/2 or push promises are not supported on a platform, the PS will
return
a mime-multipart response to the GET request, with the same content as the
push promise'

Nothing else needs to be changed - just instead of a push promise frame, it
will be a mime part.
A UA or PS can support only http/2 - but some may optionally also support
the multipart
response, and accept requests as http/1.1.

While many HTTP/2 stacks are now available, the APIs for push promises are
not very familiar
or well exposed.

This is a problem in particular for receipts, since the AS to PS
communication has to be implemented
by many developers. It will also help in the case of UA to PS, low-end IOT
devices tend to lack
http/2 support.

Costin