Add unit tests that show how to verify the source code view model

[uhafner]

Add unit tests that show the navigation to the source code view.

Starting with a CoverageBuildAction instance, one can navigate to the model of the source code view using the following code snippet:

SourceViewModel model = action.getTarget().getDynamic(link, null, null);

[codecov]

Codecov Report

Merging #269 (6b0e0eb) into master (8e8c40b) will increase coverage by 0.60%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #269      +/-   ##
============================================
+ Coverage     58.00%   58.61%   +0.60%     
- Complexity      483      490       +7     
============================================
  Files            56       56              
  Lines          2298     2298              
  Branches        289      289              
============================================
+ Hits           1333     1347      +14     
+ Misses          859      841      -18     
- Partials        106      110       +4     

Impacted Files	Coverage Δ
...ns/plugins/coverage/model/CoverageBuildAction.java	51.06% <ø> (+2.12%)	⬆️
...kins/plugins/coverage/model/CoverageViewModel.java	37.77% <ø> (+10.00%)	⬆️
...enkins/plugins/coverage/model/SourceViewModel.java	50.00% <0.00%> (+50.00%)	⬆️

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