Add Domain Name Matcher

Design difference from original vision: Skipped FQDN step to make it more generalized
#28651 (comment 2787394)

common/namematcher/matcher.go

+package namematcher
+
+import "strings"
+
+func NewNameMatcher(rule string) NameMatcher {
+	return NameMatcher{suffix: strings.TrimPrefix(rule, "^"), exact: strings.HasPrefix(rule, "^")}
+}
+
+type NameMatcher struct {
+	exact  bool
+	suffix string
+}
+
+func (m *NameMatcher) IsSupersetOf(matcher NameMatcher) bool {
+	if m.exact {
+		return matcher.exact && m.suffix == matcher.suffix
+	}
+	return strings.HasSuffix(matcher.suffix, m.suffix)
+}
+
+func (m *NameMatcher) IsMember(s string) bool {
+	if m.exact {
+		return s == m.suffix
+	}
+	return strings.HasSuffix(s, m.suffix)
+}

common/namematcher/matcher_test.go

+package namematcher
+
+import "testing"
+
+import . "github.com/smartystreets/goconvey/convey"
+
+func TestMatchMember(t *testing.T) {
+	testingVector := []struct {
+		matcher string
+		target  string
+		expects bool
+	}{
+		{matcher: "", target: "", expects: true},
+		{matcher: "^snowflake.torproject.net", target: "snowflake.torproject.net", expects: true},
+		{matcher: "^snowflake.torproject.net", target: "faketorproject.net", expects: false},
+		{matcher: "snowflake.torproject.net", target: "faketorproject.net", expects: false},
+		{matcher: "snowflake.torproject.net", target: "snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "imaginary-01-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "imaginary-aaa-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "imaginary-aaa-snowflake.faketorproject.net", expects: false},
+	}
+	for _, v := range testingVector {
+		t.Run(v.matcher+"<>"+v.target, func(t *testing.T) {
+			Convey("test", t, func() {
+				matcher := NewNameMatcher(v.matcher)
+				So(matcher.IsMember(v.target), ShouldEqual, v.expects)
+			})
+		})
+	}
+}
+
+func TestMatchSubset(t *testing.T) {
+	testingVector := []struct {
+		matcher string
+		target  string
+		expects bool
+	}{
+		{matcher: "", target: "", expects: true},
+		{matcher: "^snowflake.torproject.net", target: "^snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "^snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "testing-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "^testing-snowflake.torproject.net", expects: true},
+		{matcher: "snowflake.torproject.net", target: "", expects: false},
+	}
+	for _, v := range testingVector {
+		t.Run(v.matcher+"<>"+v.target, func(t *testing.T) {
+			Convey("test", t, func() {
+				matcher := NewNameMatcher(v.matcher)
+				target := NewNameMatcher(v.target)
+				So(matcher.IsSupersetOf(target), ShouldEqual, v.expects)
+			})
+		})
+	}
+}