Yeah, this will only work for Lyse. Sorry.

When a root twt doesn't have any known replies the URLs view didn't
provide an URL for the conversation on twtxt.net. Now it will always
generate it, so users can quickly jump over to the yarnd web UI.

Big thanks to fastidious over at
https://arrakis.netbros.com/user/fastidious/twtxt.txt for bringing up
this idea!

Usually it doesn't matter if the mentions are preceding the subject or
not. But lately I had the situations that it was more convenient to have
the subject at the very front, so it's easier to reply to all of the
mentions without moving around the text. Let's illustrate this on the
following example. Previously a reply template would look like this:

  @<hugo https://example.com/twtxt.txt> @<cathy https://example.org/twtxt.txt> (#abcdefg)

Now the order is reversed:

  (#abcdefgh) @<hugo https://example.com/twtxt.txt> @<cathy https://example.org/twtxt.txt>

So it's much easier to reply to both individually like that:

  (#abcdefgh) Oh great, @<hugo https://example.com/twtxt.txt>! @<cathy https://example.org/twtxt.txt>, exactly, that's what I was thinking too.

Text just has to be inserted in the middle without reordering subject
and mentions manually. Keep in mind that the subject can only be
preceded by mentions according to the Twt Subject Extension
(https://dev.twtxt.net/doc/twtsubjectextension.html), but no other
non-whitespace text.

According to prologic this is now the norm for yarnd. The parser already
handles them as well, so nothing to do other than changing the compose
form.

This refactoring also uncovered some kind of bug, that got masked by the
`twtxt.models.Tweet` constructor, which did the actual conversion to
seconds precision. Without that Tweet container in between anymore, two
precision-related tests failed. So this precision handling needed to be
replicated into the hash creation – where it acutally belongs. One day,
we're finally getting rid of the `twtxt.models.Tweet` entirely, so it's
not really duplicated anymore.

This is part of surgically removing the twtxt reference implementation
of tt.