Fix unable to add API specific policy using YAML format via Publisher REST API

[thisaltennakoon]

Fix wso2/api-manager#1635

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +10.03 🎉

Comparison is base (e3030f4) 39.09% compared to head (26860cf) 49.13%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #11941       +/-   ##
===========================================
+ Coverage   39.09%   49.13%   +10.03%     
===========================================
  Files        1778     1780        +2     
  Lines      127438   134818     +7380     
  Branches    18202    20999     +2797     
===========================================
+ Hits        49820    66237    +16417     
+ Misses      71369    61274    -10095     
- Partials     6249     7307     +1058     

Flag	Coverage Δ
integration_tests	43.72% <100.00%> (+12.00%)	⬆️
unit_tests	21.53% <ø> (+0.98%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...java/org/wso2/carbon/apimgt/impl/APIConstants.java	49.56% <ø> (-9.32%)	⬇️
...rest/api/publisher/v1/impl/ApisApiServiceImpl.java	30.58% <100.00%> (+17.00%)	⬆️
...isher/v1/impl/OperationPoliciesApiServiceImpl.java	41.86% <100.00%> (+40.69%)	⬆️

... and 436 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[thisaltennakoon]

Opened a new PR: #12237