feat: client | network group assignment alignment and test

[1riatsila1]

Description

Data source for network group assignments
Use get network group assignments method in resources

Related Issue(s)

[codecov]

Codecov Report

Attention: Patch coverage is 72.00000% with 28 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@9f47971). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
.../provider/data-sources/network_group_assignment.go	73.33%	12 Missing and 4 partials ⚠️
...der/provider/resources/network_group_assignment.go	47.82%	10 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #37   +/-   ##
=======================================
  Coverage        ?   36.13%           
=======================================
  Files           ?       46           
  Lines           ?     4812           
  Branches        ?        0           
=======================================
  Hits            ?     1739           
  Misses          ?     2859           
  Partials        ?      214           

Files with missing lines	Coverage Δ
pkg/config-api-provider/test/util/utils.go	100.00% <100.00%> (ø)
...der/provider/resources/network_group_assignment.go	64.94% <47.82%> (ø)
.../provider/data-sources/network_group_assignment.go	73.33% <73.33%> (ø)