support for version 8 servers

[egandro]

Pull Request type

• [ ] Bugfix
• [x] Feature
• [x] Refactoring (no functional changes, no api changes)
• [ ] Build related changes (Please run ./gradlew generateLock saveLock to refresh dependencies)
• [ ] WHOSUSING.md
• [ ] Other (please describe):

Changes in this PR

Added support for ES8.

Describe the new behavior from this PR, and why it's needed Issue #

The ES8 API for Templates has changed.

Alternatives considered

Make a ES8 folder. Since the changes are 3 lines of code to the templates and the name of the index URL I didn't want to create more copy&paste code as needed.

(Maybe the build breakes on CI/CD - then I will add this PR here, too - https://github.com/Netflix/conductor-community/pull/257)

[egandro]

This is broken :(

The libraries also needs to be updated.

Closing this PR.