Unlike your question supposes, which is declared as "general", you are mentioning Spring MVC as backend for REST-Endpoint API as well as Angular as independent frontend solution, altogether handling user, groups and their special rights on objects.
There are some dozen if not hundreds of possibilities to build an API, but I suppose you look at jhipster.tech, which is a code generator serving you the basic fundament for Spring backend and Angular frontend (you can choose other frontends, but I recommend to use Angular for generation as it is similar to Java in Spring framework).
As you can generate from easy first monolithic constructs for testing and learning all the modules and technics as well as high-level company-driving microservices for ERP including process-management and accounting, API for field workers, partner companies and clients, one or more Webstores, connecting mobile devices and everything else "in minutes", it is not only a splendid tool, that shows you best practice in development including good documentation, but it is also used as generator for professionals to start a project.
With jhipster and its community you'll learn from pro's and get some steps further - at least for me the work of those guys was and is an eye-opener - after years of reading books about programming and turning left and right, often enough to nowhere.
Of course, it is opinionated like Spring and Angular themselves. But the technics which are used are reliable, well combinated and do build the daily software-stack in many companies since and for years.
You'll code in Java or Kotlin in Spring and ECMAScript (Typescript as Javascript Transpiler) in Angular framework. The structure and ideas behind these programming languages are comparable - "Typescript is easy to understand for Java-guys". And you'll stay independent from support companies, platforms or library changes. Besides you'll learn how to update your own software, which is often forgotten in business software, too.
