Feature/#5 architecture diagram

Summary

This MR provides an architecture diagram in the README (hopefully) explaining how the back end works. Furthermore, the README now comes with an integrated TOC created with doctoc.

Use Cases

This should be useful for everyone working with oder being interested in the back end.

Documentation

It is basically documentation.

Test

Have a look at https://gitlab.gwdg.de/subugoe/ahiqar/backend/-/blob/feature/%235-architecture-diagram/README.md and test if the diagram is understandable. :)

Changelog

• I added a statement to the CHANGELOG.

Related Tickets

Closes

#5 (closed)

/cc Mathias Göbel, Frank Schneider, Michelle Weidling