Use caddy's certmagic library for extensible/robust ACME handling (#14177)

* use certmagic for more extensible/robust ACME cert handling

* accept TOS based on config option

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/miekg/dns/duplicate.go

@@ -0,0 +1,37 @@
+package dns
+
+//go:generate go run duplicate_generate.go
+
+// IsDuplicate checks of r1 and r2 are duplicates of each other, excluding the TTL.
+// So this means the header data is equal *and* the RDATA is the same. Returns true
+// if so, otherwise false. It's a protocol violation to have identical RRs in a message.
+func IsDuplicate(r1, r2 RR) bool {
+	// Check whether the record header is identical.
+	if !r1.Header().isDuplicate(r2.Header()) {
+		return false
+	}
+
+	// Check whether the RDATA is identical.
+	return r1.isDuplicate(r2)
+}
+
+func (r1 *RR_Header) isDuplicate(_r2 RR) bool {
+	r2, ok := _r2.(*RR_Header)
+	if !ok {
+		return false
+	}
+	if r1.Class != r2.Class {
+		return false
+	}
+	if r1.Rrtype != r2.Rrtype {
+		return false
+	}
+	if !isDuplicateName(r1.Name, r2.Name) {
+		return false
+	}
+	// ignore TTL
+	return true
+}
+
+// isDuplicateName checks if the domain names s1 and s2 are equal.
+func isDuplicateName(s1, s2 string) bool { return equal(s1, s2) }