Advanced data discovery with the Rucio-datalink demonstrator using recursive DataLink

This will allow visualisation tools groups in orange team (Aladin, VisiVO, etc...) to provide and support  links external to the SRC nodes such as : additional documentation, previews, derived data such as moment maps,  other formats, etc....  

The idea is that these additional links help to describe the data and to choose where and how the soda queries have to be performed

• Magenta provides "set-metadata command to add this link (URL) to the dataset metadata as a new metadata field.
• Magenta makes the rucio ObsCore DataLink service display this "recursive DataLink" link beside the full retrieval and the two SODA links.
• orange team subgroups (aladin, ....) provide these recursive DataLink services.
• Tools are able to use this "second step" DataLink service and provide advanced discovery facilities.