888 Make Apply_variant function more generic and fix issue with default value

[HenrZu]

Changes and Information

Please briefly list the changes (main added features, changed items, or corrected bugs) made:

• Currently, due to the default values for the Baseinfectiouneses, the transmission risk is always zero in the vvs example. This is now fixed since the new Tranmission risk from a new variant is given with a relative factor.
• We deleted the explicit Variant parameters
• Adjusted test data since there was an error

If need be, add additional information and what the reviewer should look out for in particular:

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Checks by code author

• Every addressed issue is linked (use the "Closes #ISSUE" keyword below)
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Checks by code reviewer(s)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cdc62ee) 95.60% compared to head (daa0ac2) 95.88%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #904      +/-   ##
==========================================
+ Coverage   95.60%   95.88%   +0.27%     
==========================================
  Files         118      118              
  Lines        9448     9397      -51     
==========================================
- Hits         9033     9010      -23     
+ Misses        415      387      -28     

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[reneSchm]

Good work, I'd like to see a few more changes.