fix: handles default case for string array IN filter for pinot handlers

[kotharironak]

Description

The default value for string column is null in pinot - https://docs.pinot.apache.org/configuration-reference/schema
So, there are cases when query can only returns null group. These cases a follow up query with empty clause as shown in the below example:

Select dateTimeConvert(start_time_millis,'1:MILLISECONDS:EPOCH','1:MILLISECONDS:EPOCH','300:SECONDS'), span_name, COUNT(*) FROM spanEventView WHERE customer_id = '__default' 
AND start_time_millis >= 1701052800000 AND start_time_millis < 1701138900000 
AND ( user_roles IN ('null') ) ) ) 
GROUP BY dateTimeConvert(start_time_millis,'1:MILLISECONDS:EPOCH','1:MILLISECONDS:EPOCH','300:SECONDS'), user_roles 
limit 1000

It could possible that given time limit window, we have only one group null.

This PR, handles the above default scenario.

Testing

Added Unit test.

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8c2c883) 73.26% compared to head (0924bf9) 73.27%.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #215   +/-   ##
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  Coverage     73.26%   73.27%           
- Complexity     1115     1116    +1     
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  Files            96       96           
  Lines          4784     4785    +1     
  Branches        547      548    +1     
=========================================
+ Hits           3505     3506    +1     
  Misses         1054     1054           
  Partials        225      225           

Flag	Coverage Δ
integration	73.27% <100.00%> (+<0.01%)	⬆️
unit	69.27% <100.00%> (+<0.01%)	⬆️

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[github-actions]

Unit Test Results

  40 files  ±0    40 suites  ±0   7s ⏱️ -4s
320 tests +1  320 ✔️ +1  0 💤 ±0  0 ❌ ±0 

Results for commit 0924bf9. ± Comparison against base commit 8c2c883.

[varsha-abhinandan]

Why is gateway service converting null string to empty ? Shouldn't be fix that instead of expecting every converter to handle this ?

[saxenakshitiz]

'null' is special case on how it is stored in Pinot and needs to be converted to an appropriate value. Isn't it?

[saxenakshitiz]

why are we handling special case only for string array? There are other array types as well. We don't need to handle this case for them?

[kotharironak]

Closing this with respect : hypertrace/gateway-service#186