openapi-generator replaced oltu with scribejava for Java

#10661

This PR replaces the deprecated Apache Oltu library with ScribeJava for the Java OkHttp client. It also tries to improve the OAuth code as follows:

uniforming the OAuth authentication to the other auth methods, managing the Authentication as a parameter instead of using an OkHttp interceptor;
introducing the AuthorizationCode, Password, and ClientCredentials Grants;
managing authorization URL, refresh URL, and scope parameters for the oauth2 config.

this replaces #10732

PR checklist

[x] Read the contribution guidelines.
[x] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
[x] Run the following to build the project and update samples:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
[ ] File the PR against the correct branch: master (5.3.0), 6.0.x
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@wing328 @bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608 @nmuesch

Nov 25 '21 20:11 valmoz

Can this PR be completed soon?

Jul 15 '22 11:07 DFromTheHood

Maybe @wing328 or @jmini could take a look?

Sep 13 '22 14:09 RockyMM

I admit that I let this PR die, I didn't have enough time to complete it. If it is still of interest, I can try to recover it, adapting it to the new versions... I don't know when I'll be able to work on it though

Sep 13 '22 14:09 valmoz

Ah, too bad, as it is a very welcome improvent. I could maybe dedicate some time in the future for this, but it is very unlikely, I guess we are all in the same boat :D

Sep 13 '22 15:09 RockyMM

Are there any plans to resurrect this branch?

Jul 20 '23 17:07 hroig

Hi @hroig unfortunately I didn't have time to dedicate to it. If I'll be able to find some time during the incoming summer I'll try to complete it, but I can't assure anything. If somebody wants to try and complete it, it could be a great help.

Jul 21 '23 12:07 valmoz

how is it going?

Sep 12 '23 09:09 chilphil

replaced oltu with scribejava for Java - okhttp client

PR checklist