feat(flux-dsl): supports empty logic operator

[bednar]

Closes #212

Proposed Changes

The FluxDSL supports empty logic operator. It is useful for something like:

String classCode = search.getClassCode();
restriction = Restrictions.and(
        Restrictions.tag("containerId").equal(search.getContainerId()),
        classCode != null ? Restrictions.tag("classCode").equal(classCode) : Restrictions.or(),
        Restrictions.measurement().equal("data")
);

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• mvn test completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)

[codecov-io]

Codecov Report

Merging #213 (b9af9a6) into master (3f5b8b8) will decrease coverage by 0.01%.
The diff coverage is 75.00%.

@@             Coverage Diff              @@
##             master     #213      +/-   ##
============================================
- Coverage     88.40%   88.39%   -0.02%     
  Complexity      447      447              
============================================
  Files           139      139              
  Lines          5513     5516       +3     
  Branches        226      227       +1     
============================================
+ Hits           4874     4876       +2     
  Misses          561      561              
- Partials         78       79       +1     

Impacted Files	Coverage Δ	Complexity Δ
.../query/dsl/functions/restriction/Restrictions.java	95.45% <75.00%> (-4.55%)	11.00 <0.00> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3f5b8b8...b9af9a6. Read the comment docs.