Add JS Scripting (Nashorn) addon to addons

[florian-h05]

When openHAB 4.0 switches to Java 17, NashornJS will be removed from core.

We should then add the JS Scripting (Nashorn) automation addon to the addons repository.

We should discuss the following questions:

• Install Nashorn by default or not? I‘d vote against it (assuming Blockly is fully ported until then, but I expect it to be) and instead install JS Scripting (GraalJS) by default, because it is much more modern and has a well documented helper library.
• Which MIME type should it use? I‘d say that Nashorn gives the application/javascript (default) MIME type to GraalJS and gets a special MIME type (comparable to what GraalJS currently has), e.g. application/javascript;version=ES5

Cc/ @rkoshak @digitaldan @J-N-K @cweitkamp @kaikreuzer @wborn (Sorry for pinging you all)

[florian-h05]

PR to add the JS Scripting (Nashorn) engine to the addons repository is now open: #14013.

[rkoshak]

I'd agree with this plan only if we have some sort of upgrade automation to go fix everyone's rules to use the swapped MIME type. I believe it was always the intent to give the official MIME to GraalVM JS at this point but it's going to break a lot of people's systems if we don't help them. I just tried the 4.0 snapshot and it didn't go well on that front.

Note: the only way to change the MIME type in a Script (i.e. stuff under Scripts in MainUI) is through the REST API or editing the JSONDB file manually. We must avoid that if at all possible.

Assuming Blockly is ported, I have no worries about not including Nashorn by default. Moving to a new version is the time to break all the things! But we need to help clean up where we can.

[florian-h05]

Note: the only way to change the MIME type in a Script (i.e. stuff under Scripts in MainUI) is through the REST API or editing the JSONDB file manually. We must avoid that if at all possible.

Yes, we need a easy to use option in the UI for that.
@rkoshak I have a PR for this: openhab/openhab-webui#1601.

Probably we should also have an option to regenerate all Blockly scripts at once, so that the user doesn't have to open each Blockly and click the save button. That is definitely something the UI needs to do.