Friend time

[iaxx]

/friendtime now: Lists all configured local times for the channel/thread. Uses native user mentions. Entries are sorted chronologically from earliest to latest local time.
/friendtime add [timezone] [user]: Registers/updates timezone. Validates IANA timezone IDs (e.g. Europe/Bucharest, America/New_York). Regular users can only register themselves, while administrators can pass the optional user parameter.
/friendtime remove [user]: Deregisters timezone. Administrators can target other users.

Needs this in the DB.

CREATE TABLE friend_time (
	id int4 NOT NULL GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
	guild_id int8 NOT NULL,
	channel_id int8 NOT NULL,
	user_id int8 NOT NULL,
	timezone varchar(100) NOT NULL,
	CONSTRAINT uq_friend_time UNIQUE (guild_id, channel_id, user_id)
);