Ensure that the brickfield backend stuff is completely covered with unit tests

This comes from MDL-69863, where it was detected that the coverage of some key elements of the tool were not covered enough (there is a zipped coverage report in that issue).

These are some numbers (% of lines covered), of the most important elements in the plugin:

• classes/event => 17%
• classes/local/areas => 29%
• classes/local/htmlchecker => 37%

So this issue is about to achieve better coverage of all those elements, and any other that can be also covered (say privacy, say... anything).

Ciao