Feature/retry logic in es2plus client

[la3lma]

Feature to fix bug/misfeature: Some times the ES2+ responds slowly, and this patch gives the client a little more time to get it right before signalling a failure.

Also some refactoring/additional documentation (based on hints from Intellij which checks for such things before committing to VCS).

[mpeterss]

What is the timeout for requests set to in the HttpClient?

[la3lma]

Timeout is set to ten seconds: httpClient: timeout: 10000ms

[la3lma]

Have submitted a new one-line PR with the change suggested by @vihangpatil. If that does the trick, I will rework this PR into a pure refactoring PR (adding documentation etc.), and remove the retry logic.