How to invite to a group from the game. Javascript SDK OK?

Question

JavaScript

We have: a game in an iframe in classmates. (JavaScript SDK), the game has an official community.
I want: to give players a message that they can join a group, for this there will be a permanent additional bun in the game. Those. to all subscribers of the group, an additional bonus goes to game resources.
Question: is there any method, a function that allows you to display a group entry window (well, that is, so that the player joins the community without leaving the game, such as the "invite friends" window). Or can this be done only in the form of an advertising message, and then checking whether the user is in the community, and if so, then give him bonuses?
Question 2: Is it allowed to send people to the community in this way? (official community of the game). Or it's against the rules.

Answer 1

At the moment, there is no such widget (there is a REST method for checking whether a player is a member of a group).
Some games open a new tab with a group, some show a group widget, but both solutions are not recommended, as they have a number of problems for the user. It is recommended to discuss this with the moderators of the game during the moderation process.