fix: ensure defaults are properly filled for a set

[aboudreault]

A recent bugfix caused a regression when filling defaults of a set type field (#309). This can be reproduced when using deck with a valid set field with values. The bootstrap_servers is defaulted to nil.

_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
``

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +34.93 🎉

Comparison is base (482d841) 17.76% compared to head (85a672b) 52.69%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #333       +/-   ##
===========================================
+ Coverage   17.76%   52.69%   +34.93%     
===========================================
  Files          69       69               
  Lines        5093     5093               
===========================================
+ Hits          905     2684     +1779     
+ Misses       4099     1834     -2265     
- Partials       89      575      +486     

Flag	Coverage Δ
2.2.1.3	46.65% <100.00%> (?)
2.2.2	17.47% <100.00%> (?)
2.3.3	17.63% <100.00%> (ø)
2.3.3.4	47.31% <100.00%> (?)
2.4.1	36.40% <100.00%> (?)
2.4.1.3	47.39% <100.00%> (?)
2.5.1.2	47.39% <100.00%> (?)
2.6.1	?
2.6.1.0	47.39% <100.00%> (?)
2.7.2	17.71% <100.00%> (ø)
2.7.2.0	48.92% <100.00%> (?)
2.8.3	17.71% <100.00%> (ø)
2.8.4.0	48.92% <100.00%> (?)
3.0.2.0	49.38% <100.00%> (?)
3.1.1	?
3.1.1.3	50.97% <100.00%> (?)
3.2.2.1	50.97% <100.00%> (?)
community	36.40% <100.00%> (+18.63%)	⬆️
enterprise	51.52% <100.00%> (?)
enterprise-nightly	50.97% <100.00%> (?)
integration	52.69% <100.00%> (+34.93%)	⬆️
nightly	?

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

Impacted Files	Coverage Δ
kong/utils.go	88.02% <100.00%> (+1.19%)	⬆️

... and 41 files with indirect coverage changes

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[aboudreault]

It would be great if we could review and merge this one today, since there is actually a regression in deck. #336 is probably also a good idea. Let me know if I can help more.