Those exist; the one I'm most familiar with is Odoo. You download it, point it at a Postgres server and start it up. It shows you a web UI which asks you for a name for a new DB and a admin password.
After that, you get a login screen of a typical web app, but almost empty, with just a menu to configure users, groups and basic company info.
From there, you can create a module (just a folder with some basic metadata) and in it write a Python class with a few fields (like a Django model), and a menu linked to it. The system takes care of generating some views for CRUD: you just click the menu and it shows you a list of records, then click on a record to see an editable form, etc.
Permissions is just a matter of configuring in the UI or writing a CSV file that says which user groups can read and/or write which class / model, or you can write more complex rules (like users of certain groups can only see records created by them, other groups can see all).
(Disclaimer: I worked for a few years for companies that developed Odoo modules, but have left the platform for a couple of years now)
After that, you get a login screen of a typical web app, but almost empty, with just a menu to configure users, groups and basic company info.
From there, you can create a module (just a folder with some basic metadata) and in it write a Python class with a few fields (like a Django model), and a menu linked to it. The system takes care of generating some views for CRUD: you just click the menu and it shows you a list of records, then click on a record to see an editable form, etc.
Permissions is just a matter of configuring in the UI or writing a CSV file that says which user groups can read and/or write which class / model, or you can write more complex rules (like users of certain groups can only see records created by them, other groups can see all).
(Disclaimer: I worked for a few years for companies that developed Odoo modules, but have left the platform for a couple of years now)