[GH-6798] added a new api endpoint to get the bulk reactions for posts (#10049)

* 6798 added a new api to get the bulk reactions for posts

* 6798 added the permsission check before getting the reactions

* GH-6798 added a new app function for the new endpoint

* 6798 added a store method to get reactions for multiple posts

* 6798 connected the app function with the new store function

* 6798 fixed the review comments

model/reaction.go

@@ -37,6 +37,22 @@ func ReactionsToJson(o []*Reaction) string {
 	return string(b)
 }
 
+func MapPostIdToReactionsToJson(o map[string][]*Reaction) string {
+	b, _ := json.Marshal(o)
+	return string(b)
+}
+
+func MapPostIdToReactionsFromJson(data io.Reader) map[string][]*Reaction {
+	decoder := json.NewDecoder(data)
+
+	var objmap map[string][]*Reaction
+	if err := decoder.Decode(&objmap); err != nil {
+		return make(map[string][]*Reaction)
+	} else {
+		return objmap
+	}
+}
+
 func ReactionsFromJson(data io.Reader) []*Reaction {
 	var o []*Reaction