Webapp for event management

I'm looking to build a webapp that allow me to offer the service of create digital invitations for any type of event but the best seller will be the weddings so I need a webapp in wich I could allow my clients to custom their invite for their event and have the posibility to send their invites by mail, whatsapp, etc. One special feature that I need is about the guest count, I need to have the functionality to be able to send invitations with a limited number of people for example the invite for the family smith allow 4 persons to join the event so for example that invite will have a QR code that allow 4 persons to be able to join in the event. This feature will have different users 1-The admin that could manage any information about the event, the invites already created and all the data. 2-The event planner or the client who buy the services who will create the invites for their guest 3-The security of the event who should be able to scan the QR code and allow to enter just the number of people that the QR allow and then "burn" the QR code so nobody else could re-use that QR. So each of the 3 roles will have different functionalities. Thats why we will need the enought security to manage users. (of course we will need the page of register/login) is there a way to create automatic a keygen? I'm working in a home page with a button to buy some packages by a button of paypal or maybe use shopify or something similar, and with that the event planners buy a package and they could start creating their events without need me to create their security key / licence key I mean a way to trigger an autokeygen after somebody bought a plan in the site and they get by mail their key to create their account and start working on their event or maybe without a keygen but the way that I was thinking to develop this is when the clients bought any package they receive a security key then create their account and in the dashboard when they are logged in the could type in their security key as a “product key” or “licence key” so with that they could start creating their event. IF YOU HAVE A BETTER IDEA PLEASE LETME KNOW THIS IS JUST MY INICIAL IDEA In summary: I want to build a software as a service for example the client bought 200 digital invitations so they will have a panel to customize text and images and the panel will have the button to share that invitation by mail, WhatsApp an things like that and when they are in the event we could use the QR codes to allow to enter just the guest that have their invite and the number allowed I will add more information soon, if you are interested please reach out to me