Enh/add auth

[MBueschelberger]

Description:

Type of change:

• Bug fix.
• New feature.
• Documentation update.

Checklist for the reviewer:

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?

Related to the implementations from this PR, a simple inclusion of the http-headers into the request-objects for the services has been added.

Since there are multiple ways to fetch and pass an access-token from a broker to an application, I think it makes sense to only pass custom headers for now when the OTEClient is launched.

E.g. if a sophisticated solution in the services requires an API-token from an identity broker, the related secret cannot be simply retrieved by basic http-logins with user/password on a script basis.

Since I do not provide a generic solution with this PR, the user needs to be able to set his own headers. A generic solution might be to complex for the time remaining in the use case.

[CasperWA]

It seems there were some changes at the top of files that seem to be the beginning of further changes that were then never made?
Also, please add the self.headers usage for all resource classes under services for all requests.

[MBueschelberger]

Hi @CasperWA, this PR is way overdue, I will take a look tomorrow ASAP.

Sorry for that!

[CasperWA]

I tried to update it as best I could, concerning the latest PR with major changes for the client implementation.
I think the major part here is to ensure headers are used throughout for the services client. I was thinking it might be nice with some optional "config" keyword-args for the client upon initialization, spitting out warnings if configuration options were given that weren't used by the client - so I set that up, but didn't thoroughly test it.

[codecov-commenter]

Codecov Report

Patch coverage: 95.12% and project coverage change: +0.33 🎉

Comparison is base (8eec3c8) 90.48% compared to head (389e2c7) 90.82%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
+ Coverage   90.48%   90.82%   +0.33%     
==========================================
  Files          25       26       +1     
  Lines         389      425      +36     
==========================================
+ Hits          352      386      +34     
- Misses         37       39       +2     

Flag	Coverage Δ
linux	90.82% <95.12%> (+0.33%)	⬆️
windows	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
otelib/backends/services/base.py	97.95% <91.66%> (-2.05%)	⬇️
otelib/backends/services/client.py	96.29% <93.75%> (-3.71%)	⬇️
otelib/backends/client.py	93.33% <100.00%> (+1.66%)	⬆️
otelib/backends/python/client.py	92.30% <100.00%> (ø)
otelib/client.py	100.00% <100.00%> (ø)
otelib/warnings.py	100.00% <100.00%> (ø)

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[CasperWA]

I added a otelib.warnings module, with a custom OTELib warning class that we can detect in the test. Also, I simplified your test a bit, reusing existing pytest fixtures and such. In theory, one could separate it in two tests (for valid and invalid config values), but ... meh.

[CasperWA]

@MBueschelberger I am unfortunately running out of work hours. Is there anything here that still needs to be addressed? Maybe one of your comments above to my review? That's about it what I can understand?
Concerning that specific comment, I think it is a bit out-of-scope for this PR, so I have no problem raising it as a separate issue and moving further discussions there? That means we should(?) be able to then merge this... :)