Refactoring options for backup and integrity check in order to simplify code

[codecov[bot]]

Codecov Report

Merging #93 into dev will increase coverage by 0.09%. The diff coverage is 50%.

@@             Coverage Diff              @@
##                dev      #93      +/-   ##
============================================
+ Coverage     50.59%   50.68%   +0.09%     
+ Complexity      120      110      -10     
============================================
  Files            15       15              
  Lines          1170     1089      -81     
  Branches        151      136      -15     
============================================
- Hits            592      552      -40     
+ Misses          526      494      -32     
+ Partials         52       43       -9

Impacted Files	Coverage Δ	Complexity Δ
...d/pontem/SerializedCloudSpannerDatabaseBackup.java	49.46% <0%> (+2.53%)	3 <0> (ø)	:arrow_down:
...ntem/CloudSpannerDatabaseBackupIntegrityCheck.java	54.28% <100%> (+0.77%)	8 <0> (-8)	:arrow_down:
...e/cloud/pontem/BaseCloudSpannerDatabaseBackup.java	87.5% <0%> (-5%)	16% <0%> (-2%)