Add keyword mutation for product (#19)

src/schema.graphql

@@ -289,9 +289,15 @@ enum Orientation {
 enum ProductGroup {
   PHOTO_WALLPAPER
   CANVAS
+  """
+  WALLPAPER is tiling
+  """
   WALLPAPER
   OLD_REMOVED
   DO_IT_YOURSELF_FRAME
+  """
+  Not used
+  """
   DESIGNER_WALLPAPER
   POSTER
   FRAMED_PRINT
@@ -396,4 +402,5 @@ type Mutation {
     productId: Int!
     markets: [ProductBlacklistingInput]
   ): Product
+  productKeywords(productId: Int!, keywordIds: [Int]): Product
 }