wip: feat(client): add optional in-memory cache to client

[floreks]

TBD

[k8s-ci-robot]

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[codecov]

Codecov Report

Attention: Patch coverage is 8.67209% with 337 lines in your changes missing coverage. Please review.

Project coverage is 36.41%. Comparing base (31d5f5d) to head (02b6776).
Report is 24 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9521      +/-   ##
==========================================
- Coverage   37.08%   36.41%   -0.68%     
==========================================
  Files         283      295      +12     
  Lines       11830    12068     +238     
  Branches      202      183      -19     
==========================================
+ Hits         4387     4394       +7     
- Misses       7168     7452     +284     
+ Partials      275      222      -53