Implement sorting of events via config file

[podliashanyk]

Related discussion #96

Depends on Uninett/zinolib#61

Implemented changes:

• Added all sorting methods that exist in Ritz TK
• Added a default sorting (the unchanged order in which server sends events)
• Added a definition for a default sorting used in curitz and by SSC (called lasttrans)
• Sorting method can only be changed via config file
• Document configurable sorting methods
• Made NTIE work with sorting (using SimpleCache from flask-caching)

Attention needed:

• to the implementation itself. Are there redundancies, smelly code etc?
• should sorting methods definitions and methods be moved somewhere else from endpoints.py?
• I have tested whether order of events matches with the ones in Ritz TK/Curitz. The original sorting methods in TK are not documented, so I had to reverse engineer them and guess what set of parameters each sorting method goes after. So a test by another person would be nice.
• do you have better names? I have followed the original naming for methods so far.

Further work:

• Make it possible to change sorting method via web UI (not a part of original implementation in Curitz)

[github-actions]

Test results

    4 files      4 suites   9s ⏱️
  38 tests   38 ✔️ 0 💤 0 ❌
152 runs  152 ✔️ 0 💤 0 ❌

Results for commit 2ba497e.

♻️ This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 63.80952% with 38 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@1cbd8b9). Learn more about missing BASE report.

Files	Patch %	Lines
src/howitz/endpoints.py	60.00%	36 Missing ⚠️
src/howitz/__init__.py	77.77%	2 Missing ⚠️

Additional details and impacted files

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  Files           ?       16           
  Lines           ?     1004           
  Branches        ?        0           
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  Hits            ?      488           
  Misses          ?      516           
  Partials        ?        0           

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[hmpf]

Will rereview after rebase.

NTS: tests, the big if