This implements both a SAML2 metadata endpoint (at
`/_matrix/saml2/metadata.xml`), and a SAML2 response receiver (at
`/_matrix/saml2/authn_response`). If the SAML2 response matches what's been
configured, we complete the SSO login flow by redirecting to the client url
(aka `RelayState` in SAML2 jargon) with a login token.
What we don't yet have is anything to build a SAML2 request and redirect the
user to the identity provider. That is left as an exercise for the reader.
* Rip out half-implemented m.login.saml2 support
This was implemented in an odd way that left most of the work to the client, in
a way that I really didn't understand. It's going to be a pain to maintain, so
let's start by ripping it out.
* drop undocumented dependency on dateutil
It turns out we were relying on dateutil being pulled in transitively by
pysaml2. There's no need for that bloat.
Server Notices use a special room which the user can't dismiss. They are
created on demand when some other bit of the code calls send_notice.
(This doesn't actually do much yet becuse we don't call send_notice anywhere)
Initial commit; this doesn't work yet - the LIKE filtering seems too aggressive.
It also needs _do_initial_spam to be aware of prepopulating the whole user_directory_search table with all users...
...and it needs a handle_user_signup() or something to be added so that new signups get incrementally added to the table too.
Committing it here as a WIP
Allows delegating the password auth to an external module. This also
moves the LDAP auth to using this system, allowing it to be removed from
the synapse tree entirely in the future.
