Prework for multiple chargers per cs

[drc38]

@lbbrhzn still a bit of work but appreciate your views on the draft.

Maintains current functionality ie 1 charger per cs but tidies up the code and will make it easier to implement multiple chargers per cs in the future.

[codecov]

Codecov Report

Attention: Patch coverage is 95.58824% with 9 lines in your changes missing coverage. Please review.

Project coverage is 94.31%. Comparing base (6e5a419) to head (5fb4b05).

Files with missing lines	Patch %	Lines
custom_components/ocpp/api.py	96.20%	3 Missing ⚠️
custom_components/ocpp/config_flow.py	92.00%	2 Missing ⚠️
custom_components/ocpp/ocppv16.py	86.66%	2 Missing ⚠️
custom_components/ocpp/__init__.py	95.65%	1 Missing ⚠️
custom_components/ocpp/chargepoint.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1480      +/-   ##
==========================================
- Coverage   94.69%   94.31%   -0.38%     
==========================================
  Files          12       12              
  Lines        1943     2042      +99     
==========================================
+ Hits         1840     1926      +86     
- Misses        103      116      +13     

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[drc38]

A release with these changes is available here: https://github.com/drc38/ocpp/releases/tag/0.8.1

[drc38]

https://github.com/drc38/ocpp/releases/tag/0.8.3

[drc38]

https://github.com/drc38/ocpp/releases/tag/0.8.4