How do i make a invite link for a multi community cad?

Hey people I’m working on a multi community CAD/MDT on bubble. I’ve seen a lot of times big roleplay cad communities like RocketCAD use inviting members on the expensive plan. It’s something which contains a sharable link which you can send to your members and it automatically approve your users. Meaning changing is Approve? = yes. I wanted to do something similar a invite link and things like that but couldn’t figure out a way. If I can seek some help from the awesome members of this forum and bubblers that know and can help me make my thing. I’ll thankful to recieve a reply from you!