diff --git a/vendor/google.golang.org/protobuf/internal/impl/legacy_enum.go b/vendor/google.golang.org/protobuf/internal/impl/legacy_enum.go
new file mode 100644
index 0000000..f7d7ffb
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/impl/legacy_enum.go
@@ -0,0 +1,219 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package impl
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+
+	"google.golang.org/protobuf/internal/filedesc"
+	"google.golang.org/protobuf/internal/strs"
+	"google.golang.org/protobuf/reflect/protoreflect"
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+)
+
+// legacyEnumName returns the name of enums used in legacy code.
+// It is neither the protobuf full name nor the qualified Go name,
+// but rather an odd hybrid of both.
+func legacyEnumName(ed pref.EnumDescriptor) string {
+	var protoPkg string
+	enumName := string(ed.FullName())
+	if fd := ed.ParentFile(); fd != nil {
+		protoPkg = string(fd.Package())
+		enumName = strings.TrimPrefix(enumName, protoPkg+".")
+	}
+	if protoPkg == "" {
+		return strs.GoCamelCase(enumName)
+	}
+	return protoPkg + "." + strs.GoCamelCase(enumName)
+}
+
+// legacyWrapEnum wraps v as a protoreflect.Enum,
+// where v must be a int32 kind and not implement the v2 API already.
+func legacyWrapEnum(v reflect.Value) pref.Enum {
+	et := legacyLoadEnumType(v.Type())
+	return et.New(pref.EnumNumber(v.Int()))
+}
+
+var legacyEnumTypeCache sync.Map // map[reflect.Type]protoreflect.EnumType
+
+// legacyLoadEnumType dynamically loads a protoreflect.EnumType for t,
+// where t must be an int32 kind and not implement the v2 API already.
+func legacyLoadEnumType(t reflect.Type) pref.EnumType {
+	// Fast-path: check if a EnumType is cached for this concrete type.
+	if et, ok := legacyEnumTypeCache.Load(t); ok {
+		return et.(pref.EnumType)
+	}
+
+	// Slow-path: derive enum descriptor and initialize EnumType.
+	var et pref.EnumType
+	ed := LegacyLoadEnumDesc(t)
+	et = &legacyEnumType{
+		desc:   ed,
+		goType: t,
+	}
+	if et, ok := legacyEnumTypeCache.LoadOrStore(t, et); ok {
+		return et.(pref.EnumType)
+	}
+	return et
+}
+
+type legacyEnumType struct {
+	desc   pref.EnumDescriptor
+	goType reflect.Type
+	m      sync.Map // map[protoreflect.EnumNumber]proto.Enum
+}
+
+func (t *legacyEnumType) New(n pref.EnumNumber) pref.Enum {
+	if e, ok := t.m.Load(n); ok {
+		return e.(pref.Enum)
+	}
+	e := &legacyEnumWrapper{num: n, pbTyp: t, goTyp: t.goType}
+	t.m.Store(n, e)
+	return e
+}
+func (t *legacyEnumType) Descriptor() pref.EnumDescriptor {
+	return t.desc
+}
+
+type legacyEnumWrapper struct {
+	num   pref.EnumNumber
+	pbTyp pref.EnumType
+	goTyp reflect.Type
+}
+
+func (e *legacyEnumWrapper) Descriptor() pref.EnumDescriptor {
+	return e.pbTyp.Descriptor()
+}
+func (e *legacyEnumWrapper) Type() pref.EnumType {
+	return e.pbTyp
+}
+func (e *legacyEnumWrapper) Number() pref.EnumNumber {
+	return e.num
+}
+func (e *legacyEnumWrapper) ProtoReflect() pref.Enum {
+	return e
+}
+func (e *legacyEnumWrapper) protoUnwrap() interface{} {
+	v := reflect.New(e.goTyp).Elem()
+	v.SetInt(int64(e.num))
+	return v.Interface()
+}
+
+var (
+	_ pref.Enum = (*legacyEnumWrapper)(nil)
+	_ unwrapper = (*legacyEnumWrapper)(nil)
+)
+
+var legacyEnumDescCache sync.Map // map[reflect.Type]protoreflect.EnumDescriptor
+
+// LegacyLoadEnumDesc returns an EnumDescriptor derived from the Go type,
+// which must be an int32 kind and not implement the v2 API already.
+//
+// This is exported for testing purposes.
+func LegacyLoadEnumDesc(t reflect.Type) pref.EnumDescriptor {
+	// Fast-path: check if an EnumDescriptor is cached for this concrete type.
+	if ed, ok := legacyEnumDescCache.Load(t); ok {
+		return ed.(pref.EnumDescriptor)
+	}
+
+	// Slow-path: initialize EnumDescriptor from the raw descriptor.
+	ev := reflect.Zero(t).Interface()
+	if _, ok := ev.(pref.Enum); ok {
+		panic(fmt.Sprintf("%v already implements proto.Enum", t))
+	}
+	edV1, ok := ev.(enumV1)
+	if !ok {
+		return aberrantLoadEnumDesc(t)
+	}
+	b, idxs := edV1.EnumDescriptor()
+
+	var ed pref.EnumDescriptor
+	if len(idxs) == 1 {
+		ed = legacyLoadFileDesc(b).Enums().Get(idxs[0])
+	} else {
+		md := legacyLoadFileDesc(b).Messages().Get(idxs[0])
+		for _, i := range idxs[1 : len(idxs)-1] {
+			md = md.Messages().Get(i)
+		}
+		ed = md.Enums().Get(idxs[len(idxs)-1])
+	}
+	if ed, ok := legacyEnumDescCache.LoadOrStore(t, ed); ok {
+		return ed.(protoreflect.EnumDescriptor)
+	}
+	return ed
+}
+
+var aberrantEnumDescCache sync.Map // map[reflect.Type]protoreflect.EnumDescriptor
+
+// aberrantLoadEnumDesc returns an EnumDescriptor derived from the Go type,
+// which must not implement protoreflect.Enum or enumV1.
+//
+// If the type does not implement enumV1, then there is no reliable
+// way to derive the original protobuf type information.
+// We are unable to use the global enum registry since it is
+// unfortunately keyed by the protobuf full name, which we also do not know.
+// Thus, this produces some bogus enum descriptor based on the Go type name.
+func aberrantLoadEnumDesc(t reflect.Type) pref.EnumDescriptor {
+	// Fast-path: check if an EnumDescriptor is cached for this concrete type.
+	if ed, ok := aberrantEnumDescCache.Load(t); ok {
+		return ed.(pref.EnumDescriptor)
+	}
+
+	// Slow-path: construct a bogus, but unique EnumDescriptor.
+	ed := &filedesc.Enum{L2: new(filedesc.EnumL2)}
+	ed.L0.FullName = AberrantDeriveFullName(t) // e.g., github_com.user.repo.MyEnum
+	ed.L0.ParentFile = filedesc.SurrogateProto3
+	ed.L2.Values.List = append(ed.L2.Values.List, filedesc.EnumValue{})
+
+	// TODO: Use the presence of a UnmarshalJSON method to determine proto2?
+
+	vd := &ed.L2.Values.List[0]
+	vd.L0.FullName = ed.L0.FullName + "_UNKNOWN" // e.g., github_com.user.repo.MyEnum_UNKNOWN
+	vd.L0.ParentFile = ed.L0.ParentFile
+	vd.L0.Parent = ed
+
+	// TODO: We could use the String method to obtain some enum value names by
+	// starting at 0 and print the enum until it produces invalid identifiers.
+	// An exhaustive query is clearly impractical, but can be best-effort.
+
+	if ed, ok := aberrantEnumDescCache.LoadOrStore(t, ed); ok {
+		return ed.(pref.EnumDescriptor)
+	}
+	return ed
+}
+
+// AberrantDeriveFullName derives a fully qualified protobuf name for the given Go type
+// The provided name is not guaranteed to be stable nor universally unique.
+// It should be sufficiently unique within a program.
+//
+// This is exported for testing purposes.
+func AberrantDeriveFullName(t reflect.Type) pref.FullName {
+	sanitize := func(r rune) rune {
+		switch {
+		case r == '/':
+			return '.'
+		case 'a' <= r && r <= 'z', 'A' <= r && r <= 'Z', '0' <= r && r <= '9':
+			return r
+		default:
+			return '_'
+		}
+	}
+	prefix := strings.Map(sanitize, t.PkgPath())
+	suffix := strings.Map(sanitize, t.Name())
+	if suffix == "" {
+		suffix = fmt.Sprintf("UnknownX%X", reflect.ValueOf(t).Pointer())
+	}
+
+	ss := append(strings.Split(prefix, "."), suffix)
+	for i, s := range ss {
+		if s == "" || ('0' <= s[0] && s[0] <= '9') {
+			ss[i] = "x" + s
+		}
+	}
+	return pref.FullName(strings.Join(ss, "."))
+}