Resolve "Add new plotter to interface with uhepp.org"

Release notes

• Add a new plotter class to create plots in JSON format and push results to uhepp hub

Details

To create plots in JSON format, enable the plotter in your visualize config.

plotFormats: json
plotter: uhepp
# Collection id, e.g. 1
plotter.uhepp.collection: 1

Credentials used for authentication with the web API are taken from the following environment variables:

• UHEPP_TOKEN containing the API token (obtain at https://uhepp.org/tokens/)
• UHEPP_API specifying the API endpoint (usually https://uhepp.org/api/)

Closes #351 (closed)