Related to #10251

The presence router docs include some sample homeserver config. At some point we changed the name of the [config option](https://github.com/matrix-org/synapse/blob/859dc05b3692a3672c1a0db8deaaa9274b6aa6f5/docs/sample_config.yaml#L104-L113), but forgot to update the docs.

I've also added `presence.enabled: true` to the example, as that's the new way to enable presence (the `presence_enabled` option has been deprecated).

This PR:

* Converts UPGRADE.rst to markdown and moves the contents into the `docs/` directory.
* Updates the contents of UPGRADE.rst to point to the website instead.
* Updates links around the codebase that point to UPGRADE.rst.

`pandoc` + some manual editing was used to convert from RST to md.

Implemented config option sso.update_profile_information to keep user's display name in sync with the SSO displayname.

Signed-off-by: Johannes Kanefendt <johannes.kanefendt@krzn.de>

This PR adds a common configuration section for all modules (see docs). These modules are then loaded at startup by the homeserver. Modules register their hooks and web resources using the new `register_[...]_callbacks` and `register_web_resource` methods of the module API.

Fixes #9778

ACME v1 has been fully decommissioned for existing installs on June 1st 2021(see https://community.letsencrypt.org/t/end-of-life-plan-for-acmev1/88430/27), so we can now safely remove it from Synapse.

Dangerous actions means deactivating an account, modifying an account
password, or adding a 3PID.

Other actions (deleting devices, uploading keys) can re-use the same UI
auth session if ui_auth.session_timeout is configured.

This doc is short but a useful guide to what the request log lines mean.

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Co-authored-by: Erik Johnston <erik@matrix.org>
Co-authored-by: Daniele Sluijters <daenney@users.noreply.github.com>

* Fix broken links in documentation

* newsfile

This is essentially an implementation of the proposal made at https://hackmd.io/@richvdh/BJYXQMQHO, though the details have ended up looking slightly different.

Signed-off-by: Aaron Raimist <aaron@raim.ist>

With the prior format, 1.33.0 / 1.33.1 / 1.33.2 got separate branches:

    release-v1.33.0
    release-v1.33.1
    release-v1.33.2

Under the new model, all three would share a common branch:

    release-v1.33

As before, RCs and actual releases exist as tags on these branches.

This better reflects our support model, e.g., that the "1.33" series had
a formal release followed by two patches / updates.

Signed-off-by: Dan Callahan <danc@element.io>

Fixes #10121

Signed-off-by: Rohan Sharma <rhnsharma5113@gmail.com>

So that they render nicely in mdbook (see #10086), and so that we no longer have a mix of structured text languages in our documentation (excluding files outside of `docs/`).

Related to: #6681, #5956, #10040

Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

Implements MSC2414: https://github.com/matrix-org/matrix-doc/pull/2414


See #8551 

Signed-off-by: Callum Brown <callum@calcuode.com>

In lieu of just always enabling the unstable spaces endpoint and
unstable room version.

Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

* Update CAPTCHA documentation to mention turning off verify origin

Signed-off-by: Aaron Raimist <aaron@raim.ist>

Signed-off-by: Jerin J Titus <72017981+jerinjtitus@users.noreply.github.com>

The previous spaces_enabled flag now defaults to true and
is exposed in the sample config.

Signed-off-by: Javier Junquera Sánchez <javier@junquera.io>

Signed-off-by: Savyasachee Jha <savya.jha@hawkradius.com>

Use a database table to hold the users that should have full presence sent to them, instead of something in-memory (#9823)

Add a config option which allows enabling opentracing by user id, eg for
debugging requests made by a test user.

MSC1772 specifies the m.room.create event should be sent as part
of the invite_state. This was done optionally behind an experimental
flag, but is now done by default due to MSC1772 being approved.

Now that cross signing exists there is much less of a need for other people to look at devices and verify them individually. This PR adds a config option to allow you to prevent device display names from being shared with other servers.

Signed-off-by: Aaron Raimist <aaron@raim.ist>

Synapse can be quite memory intensive, and unless care is taken to tune
the GC thresholds it can end up thrashing, causing noticable performance
problems for large servers. We fix this by limiting how often we GC a
given generation, regardless of current counts/thresholds.

This does not help with the reverse problem where the thresholds are set
too high, but that should only happen in situations where they've been
manually configured.

Adds a `gc_min_seconds_between` config option to override the defaults.

Fixes #9890.

Adds the `port` option with the default value to the sample config file.

Support the delete of a room through DELETE request and mark
previous request as deprecated through documentation.

Signed-off-by: Thibault Ferrante <thibault.ferrante@pm.me>

Port "Allow users to click account renewal links multiple times without hitting an 'Invalid Token' page #74" from synapse-dinsic (#9832)

This attempts to be a direct port of https://github.com/matrix-org/synapse-dinsic/pull/74 to mainline. There was some fiddling required to deal with the changes that have been made to mainline since (mainly dealing with the split of `RegistrationWorkerStore` from `RegistrationStore`, and the changes made to `self.make_request` in test code).