chore(resourcemanager): add examples

[Fyusel]

Description

relates to #1234

Checklist

• Issue was linked above
• No generated code was adjusted manually
• Changelogs
  • Changelog in the root directory was adjusted
  • Changelog(s) of the service(s) were adjusted
• VERSION file(s) of the service(s) were adjusted
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[rubenhoenle]

I would suggest to add the following line to the build.gradle file (the example one, examples/resourcemanager/build.gradle):

ext.mainClassName = 'cloud.stackit.sdk.resourcemanager.examples.ResourcemanagerExample'

This way the example can be run using ./gradlew examples:resourcemanager:execute.

---

I did the same for IaaS back then:

stackit-sdk-java/examples/iaas/build.gradle

Line 5 in 2b2e5c6

ext.mainClassName = 'cloud.stackit.sdk.iaas.examples.IaaSExample'

So the examples for IaaS can be run using ./gradlew examples:iaas:execute. I think you get the idea 😄