This commit refactors various instances of mxid matching so that there
is a single well-tested regex that can be reused everywhere. The new
regex is made to match the specification word for word, and should
hopefully rule out most over- and undermatching.
By chance, this also fixes a bug in `src/discord/interactions/ping.js`
where the autocomplete tried matching an mxid against a raw sql query
rather than the provided input.
This commit refactors various instances of mxc matching so that there
is a single well-tested regex that can be reused everywhere. The new
regex is made to match the specification word for word, and should
hopefully rule out most over- and undermatching.