Drop pkg/apihelper

[marquiz]

This PR removes the apihelper package which was an unnecessary internal interface (and complication) for accessing the Kubernetes API. The change is split into multiple preliminary steps (PRs) to make the review easier.

1. pkg/utils: move GetKubeconfig from pkg/apihelper here #1562
   This change is part of an effort to remove the pkg/apihelper package.
   GetKubeconfig is useful helper functionality shared accross the codebase
   so move it into a "safe" location.

2. topology-updater: get topology api client directly #1566
   Stop using apihelper for getting the noderesourcetopology-api client.

3. topology-updater: ditch apihelper #1567
   Stop using pkg/apihelper for accessing the Kubernetes API. Modify unit
   tests to use the fake kubernetes client instead of mocked apihelper
   interface.

4. pkg/utils: move JsonPatch from pkg/apihelper #1568

5. nfd-master: ditch apihelper #1570
   Implement some of frequently used helper functions inpackage.

   This patch also contains big changes to the nfd-master unit tests. Much
   of this is about migrating from the mocked apihelper interface to fake
   kubernetes client that provides a bit more apiserver'ish functionality.
   At the same time there is quite a bit of renaming in the tests,
   shortening and unifying naming and getting rid of the extensive usage of
   "mock" everywhere.

Fixes #1547

[k8s-ci-robot]

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[marquiz]

Depends on #1562
/hold

[marquiz]

Still on hold, next piece split into #1566

[k8s-ci-robot]

PR needs rebase.

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[marquiz]

Only #1567 pending <-- ping @PiotrProkop

[marquiz]

All dependent PRs merged, there's now only a single commit
/unhold

[marquiz]

/assign @AhmedGrati

[AhmedGrati]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: f236e53b7be0de8736a131eda4db35358e78feb4

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (33858b7) 31.15% compared to head (8a6a731) 31.15%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1561   +/-   ##
=======================================
  Coverage   31.15%   31.15%           
=======================================
  Files          62       62           
  Lines        7774     7774           
=======================================
  Hits         2422     2422           
  Misses       5108     5108           
  Partials      244      244