mathlib

30b34552 - feat(ring_theory/roots_of_unity): Restrict ring homomorphism to roots of unity (#6646)

feat(ring_theory/roots_of_unity): Restrict ring homomorphism to roots of unity (#6646) Restrict a ring homomorphism to roots of unity. Co-authored-by: tb65536 <tb65536@users.noreply.github.com>