#2 allow to export properties to C4 PlantUML files

[klu2]

This PR would be a solution for #2 by adding properties to elements and relationships.

The resulting diagram would look like that:

This functionality needs to be explicitely enabled by setting com.structurizr.export.plantuml.AbstractPlantUMLExporter#PLANTUML_ADD_PROPERTIES_PROPERTY to true

[klu2]

The content of this pull request is part of https://github.com/cloudflightio/structurizr-export-c4plantuml now which can be used as a replacement to this library. As soon as this PR is merged and released, I can remove the code from the other repository again.

There is also other code in that repo (i.e. for tagging/styling), which I could also offer as a PR then.

[simonbrowndotje]

Thanks for this. Some initial thoughts:

• Since this seems to be C4-PlantUML specific, perhaps the view set property would be better named c4plantuml.addProperties to avoid any confusion that the feature is not available for the regular PlantUML export.
• On that note though, it might make sense to have two view set properties (e.g. c4plantuml.elementProperties and c4plantuml.relationshipProperties) so that users can choose which are shown ... I can imagine some people will be less inclined to see relationship properties.

[klu2]

Thanks for this. Some initial thoughts:

• Since this seems to be C4-PlantUML specific, perhaps the view set property would be better named c4plantuml.addProperties to avoid any confusion that the feature is not available for the regular PlantUML export.
• On that note though, it might make sense to have two view set properties (e.g. c4plantuml.elementProperties and c4plantuml.relationshipProperties) so that users can choose which are shown ... I can imagine some people will be less inclined to see relationship properties.

changed the PR accordingly