feat: neatening up error handling

[1riatsila1]

Description

Make a generic error handler for errors that come from the client.
Also dropping some unused mock structs (now that we are using the actual models)

And adding a heap of test cases for errors

Related Issue(s)

https://jira.arubanetworks.com/browse/UXI-8969

[codecov]

Codecov Report

Attention: Patch coverage is 89.15663% with 18 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@84b984c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...onfig-api-provider/provider/util/error_handling.go	45.45%	16 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #41   +/-   ##
=======================================
  Coverage        ?   38.52%           
=======================================
  Files           ?       53           
  Lines           ?     7235           
  Branches        ?        0           
=======================================
  Hits            ?     2787           
  Misses          ?     4192           
  Partials        ?      256           

Files with missing lines	Coverage Δ
...config-api-provider/provider/data-sources/group.go	85.05% <100.00%> (ø)
.../provider/data-sources/network_group_assignment.go	82.43% <100.00%> (ø)
...r/provider/data-sources/sensor_group_assignment.go	83.33% <100.00%> (ø)
...pi-provider/provider/data-sources/wired_network.go	87.25% <100.00%> (ø)
...provider/provider/data-sources/wireless_network.go	88.18% <100.00%> (ø)
...kg/config-api-provider/provider/resources/group.go	81.20% <100.00%> (ø)
...der/provider/resources/network_group_assignment.go	77.37% <100.00%> (ø)
...ider/provider/resources/sensor_group_assignment.go	76.69% <100.00%> (ø)
...der/provider/resources/service_group_assignment.go	66.94% <100.00%> (ø)
...g-api-provider/provider/resources/wired_network.go	85.39% <100.00%> (ø)
... and 2 more