/reviewed-on nexedi/slapos!368

As monitor stack uses values directly from buildout convert them to buildout
safe values, otherwise the the magic !py! is not stripped.

Also add a test proving that monitor with default values is going to be
correctly configured.

The backend url can come from request in `url` and `https-url` strings.
It is validated using real caddy template configuration and by using
caddy's `-stdin`. It results with calling it on each slave having any of
those parameters.

Fixes:

 * skip tests for parts which won't be fixed
 * fix assertion for master partition
 * fix typos
 * parameterize headers depending on frontend type

This reverts commit 8e24f3ab.

QUIC has issues with client certificate authentication, detected by chance.

Enables QUIC protocol https://github.com/mholt/caddy/wiki/QUIC

/reviewed-on nexedi/slapos!360

It is application/json no text/json.

Cf nexedi/slapos!358 (comment 63538)

caddy_custom_http and caddy_custom_https are implemented and exposed
instead of apache_custom_http and apache_custom_https, but with backward
compatbility for the latter form from apache-frontend.

In TODO mark missing usage of custom http found during work on this commit.

The feature is postponed and noted in TODO.

The `gzip` declaration uses defaults, which seems reasonable.

/reviewed-on nexedi/slapos!352

While reading templates/cached-virtualhost.conf.in it seems, that
SSL-enabled host shall be exposed, but this is not true -- it is
connecting to SSL backend, but listening on non-SSL.

In order to stabilise this add assertsion to test_enable_cache
which access cached ports directly and show its functionality, thus
resolving added TODO.

apache-frontend supports correctly ssl_proxy_ca_crt for ssl-proxy-verify,
thus show it in test, still keeping expected 501 reply for caddy-frontend.

The schema shall be https, not http. It got undetected, as caddy-frontend
dies really fast with 501, while apache-frontend is able to communicate
with the backend.

Features:

 * forcediphttpsadapter for SNI
 * compatbile with apache-frontend SR
 * local server to test against
 * supervisor state checks
 * promise list checks
 * test data (to save/load textual assertions)
 * own root CA for HTTPs backend