ABC-90 Add POST /emoji/search and GET /emoji/autocomplete API endpoints (#8125)

* Add POST /emoji/search and GET /emoji/autocomplete API endpoints

* Add constant to be clearer

app/emoji.go

@@ -134,11 +134,11 @@ func (a *App) DeleteEmoji(emoji *model.Emoji) *model.AppError {
 
 func (a *App) GetEmoji(emojiId string) (*model.Emoji, *model.AppError) {
 	if !*a.Config().ServiceSettings.EnableCustomEmoji {
-		return nil, model.NewAppError("deleteEmoji", "api.emoji.disabled.app_error", nil, "", http.StatusNotImplemented)
+		return nil, model.NewAppError("GetEmoji", "api.emoji.disabled.app_error", nil, "", http.StatusNotImplemented)
 	}
 
 	if len(*a.Config().FileSettings.DriverName) == 0 {
-		return nil, model.NewAppError("deleteImage", "api.emoji.storage.app_error", nil, "", http.StatusNotImplemented)
+		return nil, model.NewAppError("GetEmoji", "api.emoji.storage.app_error", nil, "", http.StatusNotImplemented)
 	}
 
 	if result := <-a.Srv.Store.Emoji().Get(emojiId, false); result.Err != nil {
@@ -169,6 +169,18 @@ func (a *App) GetEmojiImage(emojiId string) (imageByte []byte, imageType string,
 	}
 }
 
+func (a *App) SearchEmoji(name string, prefixOnly bool, limit int) ([]*model.Emoji, *model.AppError) {
+	if !*a.Config().ServiceSettings.EnableCustomEmoji {
+		return nil, model.NewAppError("SearchEmoji", "api.emoji.disabled.app_error", nil, "", http.StatusNotImplemented)
+	}
+
+	if result := <-a.Srv.Store.Emoji().Search(name, prefixOnly, limit); result.Err != nil {
+		return nil, result.Err
+	} else {
+		return result.Data.([]*model.Emoji), nil
+	}
+}
+
 func resizeEmojiGif(gifImg *gif.GIF) *gif.GIF {
 	// Create a new RGBA image to hold the incremental frames.
 	firstFrame := gifImg.Image[0].Bounds()