Add findbugs plugin

[resilva87]

Fix #4

Add findbugs plugins (https://docs.gradle.org/current/dsl/org.gradle.api.plugins.quality.FindBugsExtension.html) for detecting nasty errors. Current level is set to default, as a best balance between effort and time/memory

[codecov-io]

Codecov Report

Merging #5 into master will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master       #5   +/-   ##
=========================================
  Coverage     76.65%   76.65%           
  Complexity      246      246           
=========================================
  Files            56       56           
  Lines           784      784           
  Branches         50       50           
=========================================
  Hits            601      601           
  Misses          152      152           
  Partials         31       31

Impacted Files	Coverage Δ	Complexity Δ
...eneric/service/impl/EndpointBackupServiceFile.java	85% <100%> (ø)	7 <0> (ø)	⬇️

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