MM-12389 Update segment library to v3 (#11472)

* Update analytics-go dependency

* Migrate from segment library v2 to v3

* Reinclude gorilla/handlers module

* Fix missing module

* Remove reference to outdated analytics module

vendor/github.com/segmentio/analytics-go/json.go

@@ -0,0 +1,87 @@
+package analytics
+
+import (
+	"reflect"
+	"strings"
+)
+
+// Imitate what what the JSON package would do when serializing a struct value,
+// the only difference is we we don't serialize zero-value struct fields as well.
+// Note that this function doesn't recursively convert structures to maps, only
+// the value passed as argument is transformed.
+func structToMap(v reflect.Value, m map[string]interface{}) map[string]interface{} {
+	t := v.Type()
+	n := t.NumField()
+
+	if m == nil {
+		m = make(map[string]interface{}, n)
+	}
+
+	for i := 0; i != n; i++ {
+		field := t.Field(i)
+		value := v.Field(i)
+		name, omitempty := parseJsonTag(field.Tag.Get("json"), field.Name)
+
+		if name != "-" && !(omitempty && isZeroValue(value)) {
+			m[name] = value.Interface()
+		}
+	}
+
+	return m
+}
+
+// Parses a JSON tag the way the json package would do it, returing the expected
+// name of the field once serialized and if empty values should be omitted.
+func parseJsonTag(tag string, defName string) (name string, omitempty bool) {
+	args := strings.Split(tag, ",")
+
+	if len(args) == 0 || len(args[0]) == 0 {
+		name = defName
+	} else {
+		name = args[0]
+	}
+
+	if len(args) > 1 && args[1] == "omitempty" {
+		omitempty = true
+	}
+
+	return
+}
+
+// Checks if the value given as argument is a zero-value, it is based on the
+// isEmptyValue function in https://golang.org/src/encoding/json/encode.go
+// but also checks struct types recursively.
+func isZeroValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+
+	case reflect.Bool:
+		return !v.Bool()
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+
+	case reflect.Struct:
+		for i, n := 0, v.NumField(); i != n; i++ {
+			if !isZeroValue(v.Field(i)) {
+				return false
+			}
+		}
+		return true
+
+	case reflect.Invalid:
+		return true
+	}
+
+	return false
+}