This reverts commit d7dbad35.

* Rate-limiting for registration

* Add unit test for registration rate limiting

* Add config parameters for rate limiting on auth endpoints

* Doc

* Fix doc of rate limiting function

Co-Authored-By: babolivier <contact@brendanabolivier.com>

* Incorporate review

* Fix config parsing

* Fix linting errors

* Set default config for auth rate limiting

* Fix tests

* Add changelog

* Advance reactor instead of mocked clock

* Move parameters to registration specific config and give them more sensible default values

* Remove unused config options

* Don't mock the rate limiter un MAU tests

* Rename _register_with_store into register_with_store

* Make CI happy

* Remove unused import

* Update sample config

* Fix ratelimiting test for py2

* Add non-guest test

This is required because the 'Server' HTTP header is not always
passed through proxies.

We will later need also to import 'register_servlets' from the
'login' module, so we un-pollute the namespace now to keep the
logical changes separate.

* Fix parsing of Content-Disposition headers

TIL: filenames in content-dispostion headers can contain semicolons, and aren't
%-encoded.

* fix python2 incompatibility

* Fix docstrings

* Move RegistrationHandler init to HomeServer

* Move post registration actions to RegistrationHandler

* Add post regisration replication endpoint

* Newsfile

This allows specifying who and what is allowed to be published onto the
public room list

If TLS is disabled, it should not be an error if no cert is given.

Fixes #4554.

It's nothing to do with refreshing the certificates. No idea why it was here.

also add tests

... basically, carry on and fall back to SRV etc.

I got fed up with always adding '@unittest.DEBUG' every time I needed to debug a test.

two reasons for this. One, it saves a bunch of boilerplate. Two, it squashes
unicode to IDNA-in-a-`str` (even on python 3) in a way that it turns out we
rely on to give consistent behaviour between python 2 and 3.

We don't want to be doing .well-known lookups on these guys.

Turns out that the library does a better job of parsing URIs than our
reinvented wheel. Who knew.

There are two things going on here. The first is that, unlike
parse_server_name, URI.fromBytes will strip off square brackets from IPv6
literals, which means that it is valid input to ClientTLSOptionsFactory and
HostnameEndpoint.

The second is that we stay in `bytes` throughout (except for the argument to
ClientTLSOptionsFactory), which avoids the weirdness of (sometimes) ending up
with idna-encoded values being held in `unicode` variables. TBH it probably
would have been ok but it made the tests fragile.

Move the Host header logic down here so that (a) it is used if we reuse the
agent elsewhere, and (b) we can mess about with it with .well-known.