Use ELK's classloader, not root classloader to discover services

[ahus1]

This will use the LayoutMetaDataService's classloader to allow for cases when this JAR and other ELK JARs are loaded in dynamic classloader.

The previous logic introduced in #789 would only work if the classes were part of the root classloader.

Closes #1108

[soerendomroes]

We will take a look at this issue next year such that this can probably be included in the upcoming 0.10.0 release.

[ahus1]

@soerendomroes - thank you for the first feedback and running the CI. I'll see if I can make the CI green for this PR in the meantime.

To add some more context: This would allow ELK to be running in with PlantUML when packaged for example in the IntellIJ AsciiDoc plugin that I maintain. I also assume it would enable the PlantUML Server.

[ahus1]

Update on my previous comment: It seems that this fails for the elkjs build. Not sure what is the best way to tackle this.

I assume the serviceloader is not used at all in JS, so a similar way to override the class for JS is the way similar to SVGImage? I didn't try it out yet, some advice would be great on how to proceed here. Or that someone with more experience with elkjs takes over on that part.

[soerendomroes]

@ahus1 Probably one can just exclude the assignment similar to this.

[ahus1]

Thank you @soerendomroes - I now see the pattern :-D

I pushed a change that now made the CI pass green in my fork (https://github.com/ahus1/elk/actions/runs/12469241806 + https://github.com/ahus1/elk/actions/runs/12469241788)