Fix: fill config defaults

[nishant95]

This has the fix applied in #302 along with resolution for #307

Added test for the bug encountered in #307 as well.

[codecov-commenter]

Codecov Report

Patch coverage: 96.29% and project coverage change: -15.17 ⚠️

Comparison is base (3ec599f) 52.85% compared to head (55f775b) 37.68%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #309       +/-   ##
===========================================
- Coverage   52.85%   37.68%   -15.17%     
===========================================
  Files          66       68        +2     
  Lines        4885     5012      +127     
===========================================
- Hits         2582     1889      -693     
- Misses       1742     2790     +1048     
+ Partials      561      333      -228     

Flag	Coverage Δ
2.1.4	35.87% <96.29%> (+1.09%)	⬆️
2.2.1.3	?
2.2.2	35.87% <96.29%> (+1.09%)	⬆️
2.3.3	36.03% <96.29%> (-0.39%)	⬇️
2.3.3.4	?
2.4.1	36.11% <96.29%> (-0.39%)	⬇️
2.4.1.3	?
2.5.1.2	?
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2.6.1	36.11% <96.29%> (-0.39%)	⬇️
2.6.1.0	?
2.7.2	36.11% <96.29%> (-0.39%)	⬇️
2.7.2.0	?
2.8.3	36.11% <96.29%> (-0.39%)	⬇️
2.8.4.0	?
3.0.2	35.55% <96.29%> (-0.38%)	⬇️
3.0.2.0	?
3.1.1	37.07% <96.29%> (-0.42%)	⬇️
3.1.1.3	?
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community	37.68% <96.29%> (-0.43%)	⬇️
enterprise	?
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Impacted Files	Coverage Δ
kong/utils.go	86.82% <96.29%> (-0.19%)	⬇️

... and 22 files with indirect coverage changes

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[pmalek]

Thanks! 👍 Some minor nits.

I'll let @rainest double check when he comes online but looks good to me.

[rainest]

Kong/kubernetes-ingress-controller#3866 trial run integrated into KIC is passing Knative and conformance now, so extra confirmation in integration that the Request Transformer configuration is no longer getting clobbered.

Kong/deck#888 now succeeds as well, where it was failing with 0.39.1

[nishant95]

this fixes #307

[aboudreault]

@nishant95 @pmalek @rainest looks like this change introduced another bug where an array is completely ignored. we can reproduce with deck and the following:

_format_version: "3.0"

plugins:
- name: kafka-log
  enabled: false
  config:
    topic: konnect.auditlogs.gateway-access-logs
    bootstrap_servers:
    - host: broker-1.endpoint
      port: 9096
    - host: broker-1.endpoint
      port: 9096
    - host: broker-1.endpoint
      port: 9096
    authentication:
      strategy: sasl
      mechanism: SCRAM-SHA-512
      user: sasl_user
      password: xxxxxxxx
    security:
      ssl: false
    cluster_name: konnect-msk

with deck v1.21.0 and go-kong 0.41.0+, bootstrap_serversis set to null

[aboudreault]

ref: #333

[nishant95]

@aboudreault #309 only adds handling for subconfig of type "array", how does this cause a subconfig of type "set" to fail?
How was this working before this PR was merged?

Also, the handle_missing_fields in lua code and FillPluginsDefaults in go-kong seems out of sync. We recently faced an issue in case of non-required subconfig of type record (Testing the fix, yet to raise a PR).
Kong kept the default as nil but KIC filled the default with a record with nil fields causing KIC to be stuck in sync retry loop and ultimately getting OOMKilled. Issue: #334

[nishant95]

@pmalek @rainest @aboudreault
Fix for #334: #336