[CTM-1126] Update workflows to build, archive & download maven repo

[mvoigt-sag]

• so the build is working now: https://github.com/SoftwareAG/cumulocity-clients-kotlin/actions/runs/8919835785
• obviously the changes in the build file need to go into https://github.softwareag.com/IOTA/openapi-sdk-generator/blob/main/src/main/xtend/com/softwareag/mobile/c8y/codegen/client/kotlin/impl/BuildFileGenerator.xtend
• furthermore we need to discuss which settings/property we need/want to set: https://docs.gradle.org/current/userguide/publishing_maven.html#sec:modifying_the_generated_pom
  -- @joerghartmann what do you think?
  -- I'll also consult the Core team to hear what they think ...

[MarkJMReynolds-SAG]

Seems reasonable to me.

[joerghartmann]

@mvoigt-sag Do we need the show content tasks?

[mvoigt-sag]

@mvoigt-sag Do we need the show content tasks?

you're right, of course we dont need it, it was just for debugging...
furthermore we dont need the changes in build-jar.gradle in this PR but in the generator repo, so I created this one: https://github.softwareag.com/IOTA/openapi-sdk-generator/pull/299