Initial support for ban syncing + minor improvements and bugfixes

[funderscore1]

Few improvements to the bridge:

Change format for bridging file uploads and codeblocks to something more natural to IRC users
For file uploads:

<f_[mtrx]> https://matrix.org/_matrix/media/v3/download/something/some-other-thing/image.png (20KiB)

For code blocks:

<f_[mtrx]> https://matrix.org/_matrix/media/v3/download/something/some-other-thing

Change default format for replies, again, to something that's a bit more natural
New format:

<f_[mtrx]> f_: "hi everyone!..." <- hi!

Handle replying to self
New format (long):

<f_[mtrx]> <f_[mtrx]> what is this
<f_[mtrx]> ^

Use "`" instead of an "M" when the nick starts with an invalid character
This is more in-line with what a usual IRC user would do, and less noticeable.

Fix bug when replying to a long message
See #1521

In !cmd, don't require commands be uppercase
IRC commands are, for the most part, case-insensitive. For example, with NICK:

NICK funderscore1
:funderscore123!~0@4G4AABC5T.tor-irc.dnsbl.oftc.net NICK :funderscore1
nick funderscore12
:funderscore1!~0@4G4AABC5T.tor-irc.dnsbl.oftc.net NICK :funderscore12
Nick funderscore1
:funderscore12!~0@4G4AABC5T.tor-irc.dnsbl.oftc.net NICK :funderscore1
NIcK funderscore12
:funderscore1!~0@4G4AABC5T.tor-irc.dnsbl.oftc.net NICK :funderscore12

Or PING:

Ping :D
:helix.oftc.net PONG helix.oftc.net :D
PING :D
:helix.oftc.net PONG helix.oftc.net :D
pIng :D
:helix.oftc.net PONG helix.oftc.net :D
ping :D
:helix.oftc.net PONG helix.oftc.net :D

Fix a formatting issue in !help

Doesn't need much explanation.

Initial support for bridging Matrix bans to IRC

This is the big one. The bridge used to treat matrix bans as kicks, thus only kick the IRC user that has been banned on Matrix.

This resulted in IRC users still annoying other IRC users while the Matrix side didn't notice anything at all.

Now, matrix bans are bridged as /mode +b ${nick}!*@* and /kick ${nick}. Unbanning is still unimplemented, so moderators will need to manually send a raw command to the admin room: !cmd mode #channel -b ${nick}!*@*.

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Feedback welcome!

[funderscore1]

This is now ready for review.

[funderscore1]

ping?

[funderscore1]

gentle ping - could anyone review this please?

[tadzik]

Sorry for the long wait.

I generally agree with everything, there's just a few nitpicks. Nice work!

Can we get test to selfReplyTemplate as well? Should be easy enough to cargo-cult the other ones. This would give us an excuse to cover the 4th case (the one that's currently a compilation error).

[tadzik]

LGTM but we're failing all sorts of tests

[tadzik]

Plenty of test regressions here. Tricky to track down, since we're changing so many things at once.

Test "should allow arbitrary IRC commands to be issued" fails presumably due to command casing changes in 7956631

fb0a326 changes some Matrix->IRC messages from emote to message, which trips up the tests that expect action instead of message. This manifests itself as a timeout, since the expected "action" never arrives, so the tests waits too long.

I know it's late in the process, but I think it'd make sense to split this PR into a few smaller ones, so that the big features (like the ban syncing) don't block the minor things (like case-insensitive command handling). Not only it'll make it obvious what broke which test, it'll make the changelog much neater – we currently expect these to be a single item pointing to a single PR, and mega-PRs like this one would make it a lot trickier to process.

[tadzik]

One linting error away and the changelog, and we should be good to go

[tadzik]

I've split it into #1821, #1822 and #1823, hopefully I didn't miss anything.