Feature #70/multi charging events

[mosc5]

Fixes #70

This PR should be merged after #105

Changes proposed in this pull request:

• Avoid too many vehicles charging at once. Implement basic case, if at any point during the planned charging event the number of possbile chargees is exceeded at a Location, the charging event will be denied

The following steps were realized (required):

• Correct linting and formatting with flake8 src & mypy src & black src
• Check if tests pass locally with pytest
• Run tox
• Add the description of your changes to the CHANGELOG.md in subsection with release name v0.0.0-alpha - 2022-04-28 and state the PR number with #

Also the following steps were realized if applicable:

• Write docstrings to your code
• Write test(s) for new patch of code