Description

This PR does the following things:

Changes capacity up to which components are integrated into certain voltage levels
Generators, heat pumps and storage units are integrated into the grid based on their installed capacity instead of voltage level and only up to 20 MW.
Adds integrity checks for DSM and HeatPump class
Adds resistive heaters

Type of change

Please delete options that are not relevant.

[x] Breaking change (fix or feature that would cause existing functionality to not work as expected)

[x] New and adjusted code is formatted using the pre-commit hooks
~~New and adjusted code includes type hinting now~~
[x] I have commented my code, particularly in hard-to-understand areas
~~I have made corresponding changes to the documentation~~
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[x] The Read the Docs documentation is compiling correctly
~~If new packages are needed, I added them the setup.py, and if needed the rtd_requirements.txt, the eDisGo_env.yml and the eDisGo_env_dev.yml.~~
~~I have added new features to the corresponding whatsnew file~~