disable modifiable collection transformer for Maps

[li-ukumar]

What

Removing modifiable collections for Map type in avro codegen

Why

Maps, unlike Lists, have a key of charseq type which always need to be converted to Utf8 for avro1.4 support. But we cannot apply the same operation to the value. Hence removing this from codegen.

Test

Updated unit test

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.22%. Comparing base (2fd93ac) to head (5d1ffec).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #554      +/-   ##
============================================
- Coverage     46.24%   46.22%   -0.02%     
+ Complexity     4619     4595      -24     
============================================
  Files           412      410       -2     
  Lines         28679    28594      -85     
  Branches       4686     4677       -9     
============================================
- Hits          13262    13218      -44     
+ Misses        13834    13800      -34     
+ Partials       1583     1576       -7     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.