Add classifyCollection endpoint to NLC

[lpatino10]

Recently, the NLC service added an endpoint called classifyCollection. This PR adds that service method, along with any associated models. Unit and integration tests were also added.

[codecov-io]

Codecov Report

Merging #909 into develop will increase coverage by <.01%.
The diff coverage is 67.34%.

@@              Coverage Diff              @@
##             develop     #909      +/-   ##
=============================================
+ Coverage      65.84%   65.84%   +<.01%     
- Complexity      2613     2621       +8     
=============================================
  Files            547      551       +4     
  Lines          14073    14122      +49     
  Branches         817      818       +1     
=============================================
+ Hits            9266     9299      +33     
- Misses          4393     4409      +16     
  Partials         414      414

Impacted Files	Coverage Δ	Complexity Δ
...e_classifier/v1/model/CreateClassifierOptions.java	57.5% <ø> (ø)	5 <0> (ø)	⬇️
...guage_classifier/v1/NaturalLanguageClassifier.java	62.5% <100%> (+4.68%)	9 <1> (+1)	⬆️
...l_language_classifier/v1/model/CollectionItem.java	25% <25%> (ø)	1 <1> (?)
..._classifier/v1/model/ClassificationCollection.java	25% <25%> (ø)	1 <1> (?)
...classifier/v1/model/ClassifyCollectionOptions.java	68.96% <68.96%> (ø)	3 <3> (?)
...al_language_classifier/v1/model/ClassifyInput.java	75% <75%> (ø)	2 <2> (?)

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