add tests for SearchParameterRepositoryGenerated.kt

[epicadk]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #854

Description
Clear and concise code change description.

Added tests for SearchParameterRepositoryGenerated.kt
Made minor changes to Kdocs

Alternative(s) considered
Have you considered any alternatives? And if so, why have you chosen the approach in this PR?

Type
Choose one: Testing

Screenshots (if applicable)

Checklist

• I have read and acknowledged the Code of conduct
• I have read How to Contribute
• I have read the Developer's guide
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally
• I have built and run the reference app(s) to verify my change fixes the issue and/or does not break the reference app(s)

[epicadk]

I tried inlining this but kotlin poet won't allow it.

[codecov]

Codecov Report

Merging #905 (f7e547c) into master (7323e5c) will increase coverage by 55.29%.
The diff coverage is 70.00%.

@@              Coverage Diff              @@
##             master     #905       +/-   ##
=============================================
+ Coverage     33.36%   88.66%   +55.29%     
+ Complexity      458      457        -1     
=============================================
  Files           108      105        -3     
  Lines          9033     8981       -52     
  Branches        560      552        -8     
=============================================
+ Hits           3014     7963     +4949     
+ Misses         5732      733     -4999     
+ Partials        287      285        -2     

Impacted Files	Coverage Δ
...ogle/android/fhir/datacapture/DataCaptureConfig.kt	75.00% <66.66%> (-25.00%)	⬇️
...android/fhir/datacapture/mapping/ResourceMapper.kt	80.90% <71.42%> (-0.10%)	⬇️
...va/com/google/android/fhir/db/impl/DatabaseImpl.kt	83.63% <0.00%> (-1.82%)	⬇️
...d/fhir/index/SearchParameterRepositoryGenerated.kt	98.90% <0.00%> (+83.49%)	⬆️

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[jingtang10]

Great job @epicadk!

Just one comment to address - after that please feel free to merge.