Function format_timetz 

pub fn format_timetz(us: i64, offset_secs: i32) -> String

v7.17.0 Phase 3.P0-34 — PG TIMETZ canonical text form HH:MM:SS[.ffffff]±HH[:MM]. Mirrors PG timetz_out. The offset uses ±HH for whole-hour offsets and ±HH:MM for sub-hour offsets (matching PG’s “minimal display” rule).