Add new flux command sleep #495

[TobiasNx]

Resolves #495

[TobiasNx]

@fsteeg could you have a look, if this would be way worth to continue

[fsteeg]

Basic idea looks good. Some issues:

• PR description should reference the issue using closing keywords
• I'd copy an existing module, e.g. ObjectExceptionCatcher to get the types right (current build: does not compile cannot find symbol [...] class T)
• Formatting is off (comments), would also be avoided by copying an existing module
• I think the flux command should be just sleep
• The flux command needs to be added in src/main/resources/flux-commands.properties
• The Thread.sleep needs to be wrapped in a try-catch-block, handling InterruptedException, see e.g. in the OERSI SitemapReader

[TobiasNx]

Basic idea looks good. Some issues:

* PR description should reference the issue using closing keywords

* I'd copy an existing module, e.g. ObjectExceptionCatcher to get the types right (current build: does not compile `cannot find symbol [...] class T`)

* Formatting is off (comments), would also be avoided by copying an existing module

* I think the flux command should be just `sleep`

* The flux command needs to be added in `src/main/resources/flux-commands.properties`

* The `Thread.sleep` needs to be wrapped in a try-catch-block, handling `InterruptedException`, see e.g. in the OERSI [SitemapReader](https://gitlab.com/oersi/oersi-etl/-/blob/master/src/main/java/oersi/SitemapReader.java?ref_type=heads#L65)

Thanks I adjusted as suggested.
It is missing java tests. I am not sure how to add them for this specific function.

[blackwinter]

Would it make sense to enable this command to also support the Fix function use case? Just add another setter for the time unit and extract the sleep "action" into a dedicated method. Then we could easily reuse this class to implement the corresponding Fix function (see Catmandu).