Context

Consolidates the work from epic GODRIVER-3953 (DRIVERS-3329), this ticket (DRIVERS-3632), and GODRIVER-4173 (DRIVERS-3664) into one implementation.

Definition of Done

Spec sync

• DRIVERS-3329: https://github.com/mongodb/specifications/commit/6f64d0ee3ae49edbdb30eb995f3e29549e8cfa6a
  and https://github.com/mongodb/specifications/commit/131ab56f64916380f959bb2423a4842bce519e79
  (the latter also defines how to use and parse the public suffix list)
• DRIVERS-3632: https://github.com/mongodb/specifications/commit/5036f26e816ed2c2f08f87726bd01f9f62087b3a
• DRIVERS-3664: https://github.com/mongodb/specifications/commit/3a0ed901fd95ab2dc17a2652c33ce8779b7fb4e1 (two new prose tests)

Implementation

• Support the srvAllowedHostsSuffix option (GODRIVER-3953 / DRIVERS-3329).
• The public suffix list as a deny list as a safeguard (GODRIVER-3953 / DRIVERS-3329).
• Add docs explaining the option and the security implications of using it (GODRIVER-3953 / DRIVERS-3329).
• Introduce custom srvHostValidator callbacks (GODRIVER-4130 / DRIVERS-3632).
• Prose tests:

  Prose test	Ticket
  PSL #1–5	DRIVERS-3568
  PSL #6	GODRIVER-3953 / DRIVERS-3329
  polling #14–15	GODRIVER-4130 / DRIVERS-3632
  initial-dns #5–13	GODRIVER-4130 / DRIVERS-3632
  initial-dns #14–15	GODRIVER-4173 / DRIVERS-3664

Documentation

• SetSRVAllowedHostsSuffix and SetSRVHostValidator godoc each carry the spec-mandated warning. The spec uses MUST: "drivers MUST document that this parameter is a dangerous option."