Auto installation system on cms hosting, and creating shared access to it and linking a 3rd level domain?

Question

CMS

Good afternoon guys!
Let me explain with an example what I want to do. A client visits my website, wants to order a business card or corporate website. First, selects a design template from the list, enters company data, contacts, company name, etc. and sends an application. The system records all these data and an application appears in the project admin panel. After moderation, the manager clicks to create a demo site. The system automatically allocates space on the server for shared hosting, installs our cms with the desired design and creates a 3rd level domain for viewing the demo site.
And what is the best way to implement it? What tools?
ps: I have never done such projects before, I have almost no experience in administering servers, I know linux, but not as an admin.
I have web development experience.

Answer 1

ispmanager - hosting management
, and you can also add ansible so that it uploads demo sites...
Well, that's all ;)

Answer 2

https://10.10.10.10/manager/ispmgr?out=xml&auth=21...
Somehow you can create a user, then create a website for him (well, you just need to get a token first). When creating a site, you can specify which cms to put on the site (you need to write an aps script if you have your own cms, but it seems to be easy there). Well, or just create an "empty" site, database and fill in the files of the desired cms with the desired template in any way.