Encapsulate more than just PRIVMSG

[SoniEx2]

Currently, OTR only consistently encapsulates PRIVMSG. It should be possible to additionally convey NOTICE and TAGMSG over the encrypted channel.

For example, some messages look like this with current OTR:

@+example-client-tag=example-value PRIVMSG foo :?OTR:...
@+example-client-tag=example-value NOTICE foo :not usually encrypted
@+example-client-tag=example-value TAGMSG foo

but should ideally look like this with OTRv4:

PRIVMSG foo :?OTR:...
PRIVMSG foo :?OTR:...
PRIVMSG foo :?OTR:...

with the contents of the client-only tag, as well as the message type, encapsulated into the encrypted channel.

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References:

• hexchat-otr: https://github.com/TingPing/hexchat-otr/blob/master/src/hexchat_otr.c#L312-L314 no handling of NOTICE at all, as well as no handling of /me
• irssi:
  • actually handles /me, altho arguably badly: https://github.com/irssi/irssi/blob/master/src/otr/otr-module.c#L126
  • but no handling of NOTICE either.

[SoniEx2]

One option would be to use a TLV for NOTICEs and TAGMSGs and another TLV for client-only tags. This seems reasonable, and send some text like "Your OTR plugin does not support this message. Please update your OTR plugin." in the main stream when the NOTICE/TAGMSG TLV is used.

So these:

@+example-client-tag=example-value PRIVMSG foo :some text
@+example-client-tag=example-value NOTICE foo :some other text
@+example-client-tag=example-value TAGMSG foo

would become something like this when OTR-encrypted:

{"message": "some text", "TLVs": {"message-tags": "+example-client-tag=example-value"}}

{"message": "Your OTR plugin does not support this message. Please update your OTR plugin.", "TLVs": {"message-ext": "NOTICE some other text", "message-tags": "+example-client-tag=example-value"}}

{"message": "Your OTR plugin does not support this message. Please update your OTR plugin.", "TLVs": {"message-ext": "TAGMSG", "message-tags": "+example-client-tag=example-value"}}