Ok, so I want to develop an ed tech Saas product that is similar to Shopify regarding features like every user having their own separate site (in Shopify it is a storefront). I have no idea where to begin (I don’t even know what they call these type of products) Here are my design/architectural uncertainties:

1.) How does the software work that enables each client of mine to have their own separate site (in Shopify’s case it is a storefront)? Obviously there is generic functionality, which is the essence of the product, but each user has their own running instance of this software/site and they can customise certain things like templates/markup, branding, settings, etc. How is this possible in Elixir + Phoenix? Should I develop a regular phoenix website (the core product) and then have a script to make a copy of that site for each user that signs up? Then I will have to manage many running instances of the same site essentially. Furthermore, how will the database (Ecto repo) and assets management work? For customers to change markup/templates/store appearance, assets have to be changed.

2.) How can I enable customers to “point” a domain name at their running instance/site so that they do not have to use it with my saas product’s domain? For instance, they register at mysaasproduct.com, but they want to use a custom domain that they bought for their site, even though it is hosted on our servers. How does that work?

3.) How can I make this system pluggable? For instance, the core product could perhaps be extended with a messaging/crm/analytics plugin that will be sold separately. What design patterns and considerations should I be aware of to build a system like this. I am especially confused about how a plugin that has its own ecto repo/tables can plug into a system (the core product/site) that already has its own repo/tables.

Please note that I am not a professional developer and all this is just an ambition and curiosity that I have. I am well aware that I will probably need assistance to build such a site, but I am looking for concrete examples and resources that show how a site like this works internally to start my research journey. If anyone is aware of such a codebase or has any experience that they would like to share, please do so.

Thank you all for your time to help a less experienced member