Implement a parser for ircv3 and add unit tests to it.
Review Request #1874 — Created Oct. 1, 2022 and submitted — Latest diff uploaded
This change got pretty big so I didn't implement unescapping tags yet. I did
however put the unit tests in for escaped tags, but they are currently #if 0'd
out.The unit tests are based on the msg-split test cases from https://github.com/ircdocs/parser-tests/blob/master/tests/msg-split.yaml
Ran the unit tests.