[APIv4] add getChannelMembersTimezone (#9286)

* add getChannelMembersTimezone

* update per feedback review

* add delimeter to error

api4/channel.go

@@ -33,7 +33,7 @@ func (api *API) InitChannel() {
 	api.BaseRoutes.Channel.Handle("", api.ApiSessionRequired(deleteChannel)).Methods("DELETE")
 	api.BaseRoutes.Channel.Handle("/stats", api.ApiSessionRequired(getChannelStats)).Methods("GET")
 	api.BaseRoutes.Channel.Handle("/pinned", api.ApiSessionRequired(getPinnedPosts)).Methods("GET")
-
+	api.BaseRoutes.Channel.Handle("/timezones", api.ApiSessionRequired(getChannelMembersTimezones)).Methods("GET")
 	api.BaseRoutes.ChannelForUser.Handle("/unread", api.ApiSessionRequired(getChannelUnread)).Methods("GET")
 
 	api.BaseRoutes.ChannelByName.Handle("", api.ApiSessionRequired(getChannelByName)).Methods("GET")
@@ -821,6 +821,26 @@ func getChannelMembers(c *Context, w http.ResponseWriter, r *http.Request) {
 	w.Write([]byte(members.ToJson()))
 }
 
+func getChannelMembersTimezones(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireChannelId()
+	if c.Err != nil {
+		return
+	}
+
+	if !c.App.SessionHasPermissionToChannel(c.Session, c.Params.ChannelId, model.PERMISSION_READ_CHANNEL) {
+		c.SetPermissionError(model.PERMISSION_READ_CHANNEL)
+		return
+	}
+
+	membersTimezones, err := c.App.GetChannelMembersTimezones(c.Params.ChannelId)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	w.Write([]byte(model.ArrayToJson(membersTimezones)))
+}
+
 func getChannelMembersByIds(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.RequireChannelId()
 	if c.Err != nil {