add assertions for histograms and helper for provision time

[MatousJobanek]

Adds:

• assertions for histograms
• helper function to set the request-received-time annotation in the expected format

depends on codeready-toolchain/api#464

SANDBOX-957

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.52%. Comparing base (139ef30) to head (c5080a2).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #461   +/-   ##
=======================================
  Coverage   78.52%   78.52%           
=======================================
  Files          49       49           
  Lines        2449     2449           
=======================================
  Hits         1923     1923           
  Misses        474      474           
  Partials       52       52           

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud