Use mattermost v5 module (#1192)

vendor/github.com/mattermost/go-i18n/i18n/translation/single_translation.go

@@ -0,0 +1,61 @@
+package translation
+
+import (
+	"github.com/mattermost/go-i18n/i18n/language"
+)
+
+type singleTranslation struct {
+	id       string
+	template *template
+}
+
+func (st *singleTranslation) MarshalInterface() interface{} {
+	return map[string]interface{}{
+		"id":          st.id,
+		"translation": st.template,
+	}
+}
+
+func (st *singleTranslation) MarshalFlatInterface() interface{} {
+	return map[string]interface{}{"other": st.template}
+}
+
+func (st *singleTranslation) ID() string {
+	return st.id
+}
+
+func (st *singleTranslation) Template(pc language.Plural) *template {
+	return st.template
+}
+
+func (st *singleTranslation) UntranslatedCopy() Translation {
+	return &singleTranslation{st.id, mustNewTemplate("")}
+}
+
+func (st *singleTranslation) Normalize(language *language.Language) Translation {
+	return st
+}
+
+func (st *singleTranslation) Backfill(src Translation) Translation {
+	if (st.template == nil || st.template.src == "") && src != nil {
+		st.template = src.Template(language.Other)
+	}
+	return st
+}
+
+func (st *singleTranslation) Merge(t Translation) Translation {
+	other, ok := t.(*singleTranslation)
+	if !ok || st.ID() != t.ID() {
+		return t
+	}
+	if other.template != nil && other.template.src != "" {
+		st.template = other.template
+	}
+	return st
+}
+
+func (st *singleTranslation) Incomplete(l *language.Language) bool {
+	return st.template == nil || st.template.src == ""
+}
+
+var _ = Translation(&singleTranslation{})