fix: respect configured generator URL in swagger config

[fgreinacher]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: 3.0.0 branch for changes related to OpenAPI spec 3.0. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

During the work for #11711 I recognized that the generated OpenAPI spec does not reflect the GENERATOR_HOST which causes wrong generated code and non-functional snippets in the UI.

This PR improves that by passing on the relevant parts to the swagger config.

🛠 with ❤ at Siemens

[fgreinacher]

@frantuma As you got some context here, would you have a look?

[fgreinacher]

@frantuma Thanks a ton for merging that quickly! Can you already estimate when this will be released?

[frantuma]

@fgreinacher no fixed ETA, probably within 2 weeks

[fgreinacher]

@fgreinacher no fixed ETA, probably within 2 weeks

@frantuma Don't wanna push too hard here, but do you already have an idea about the next release data? Forget that, I just found out that the base path is not applied proplerly. Working on a fix...