Adjust documentation

[zrgt]

As the documentation is automatically generated with swagger-codegen, but the code was adjusted to work with Basyx-Python-SDK models, the documentation is not valid anymore.

We should do the following

• Remove docs
• Remove test as not used
• Adjust README.md:
  • Delete everything after "Documentation for API Endpoints"
  • Add red big banner, that we generated the client with swagger-codegen, but replaced generated models with models from Basyx-Python-SDK. It means that user can put objects created with Basyx-Python-SDK such as basyx.aas.model.Submodel("some_id") directly into Client functions.