Fix preview test

The old test expected an incorrect wrapping due to the preview function
not using unicode properly, so it got the wrong length.

Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>

Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>

Updates to the README

preview_url_resource: Ellipsis must be in unicode string

Minor updates post-review

The demo client isn't really fit for purpose, so stop encouraging people to use
it.

Add some syntax highlighting

- remove redundant "where's the spec" section: this would belong in "About
matrix", but it's already there.

- E2E is in beta rather than dev

Fix a couple of broken links

Move some bits of the README around. No words were changed in the making of
this commit.

Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>

this is rst so name it accordingly

Stop generating refresh_tokens

Remove refresh_token reference

We might as well treat all refresh_tokens as invalid. Just return a 403 from
/tokenrefresh, so that we don't have a load of dead, untestable code hanging
around.

Still TODO: removing the table from the schema.

More intelligent Content-Type parsing

Stop putting a time caveat on access tokens

Content-Type is allowed to contain options (`; charset=utf-8`, for
instance). We should allow that.

Update comments in verify_macaroon

Implement E2E for guests

The 'time' caveat on the access tokens was something of a lie, since we weren't
enforcing it; more pertinently its presence stops us ever adding useful time
caveats.

Let's move in the right direction by not lying in our caveats.

Let pip install multiple packages at once

Pip can install multiple dependencies at the same time, so there is no need to
use xargs -n1. It's significantly slower with -n1, so let's not do it with no
reason.

Since we're not doing refresh tokens any more, we should start killing off the
dead code paths. /tokenrefresh itself is a bit of a thornier subject, since
there might be apps out there using it, but we can at least not generate
refresh tokens on new logins.

Remove redundant list of known caveat prefixes

Expose /devices, /keys, and /sendToDevice to guest users, so that they can use
E2E.

We need to create devices for guests so that they can use e2e, but we don't
have anywhere to store it, so just use a fixed one.

Correctly handle 500's and 429 on federation