Services and bots were introduced with only +i. Give them the standard services
umodes, configurable via [server] service_modes (default "iHkBT"): invisible,
hideoper, servprotect — unkillable/unkickable by opers, which the ircd accepts
because the services server is U-lined — bot, and block-CTCP.
Verified live: ChanServ now whoises as "is a bot" (+B) and every pseudo-client
still links cleanly, so every mode was accepted.