Remove deprecated delete room admin API,
`POST /_synapse/admin/v1/rooms/<room_id>/delete`

* Labeled a lot more code blocks with the appropriate type
* Fixed a couple of minor typos (missing/extraneous commas)

Signed-off-by: Sumner Evans <me@sumnerevans.com>

URL cache files are short-lived and it does not make sense to offload
them (eg. to the cloud) or back them up.

Also refactors some of the registration of endpoints on workers.

When a user deletes an email from their account it will
now also remove all pushers for that email and that user
(even if these pushers were created by a different client)

Co-authored-by: Patrick Cloke <patrickc@matrix.org>

Several configuration sections are using separate settings for custom template directories, which can be confusing. This PR adds a new top-level configuration for a custom template directory which is then used for every module. The only exception is the consent templates, since the consent template directory require a specific hierarchy, so it's probably better that it stays separate from everything else.

Signed-off-by: Marcus Hoffmann <bubu@bubu1.eu>
Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

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

Port the third-party event rules interface to the generic module interface introduced in v1.37.0

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

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.