Add EMODnet Chemistry contaminants WFS about emodnetwfs

[salvafern]

Quick chat with @bart-v : the most authoritative source for WFS is still https://github.com/EMODnet/Web-Service-Documentation/, so the endpoint at the moment would be https://geoserver.hcmr.gr/geoserver/EMODNET_SHARED/wfs?SERVICE=WFS&REQUEST=GetCapabilities&VERSION=2.0.0

We should update emodnet_wfs()

relates to #139

[maelle]

@annakrystalli the service is listed with the URL https://nodc.ogs.trieste.it/geoserver/Contaminants/wfs

• which URL is correct?
• can we close this issue?

[maelle]

@annakrystalli friendly reminder about this issue for when you've got time 😸

[maelle]

@salvafern this is something the discussion in #129 could help with

[maelle]

We're currently getting an error for this web service. @bart-v is it a known problem? What is the official URL of the service?

Error in names(namespaces) <- rep("", length(namespaces)) : 
  attempt to set an attribute on NULL
Backtrace:
  1. EMODnetWFS::emodnet_get_wfs_info(service = "chemistry_contaminants")
  5. EMODnetWFS (local) `<fn>`(service = "chemistry_contaminants")
  7. EMODnetWFS::emodnet_init_wfs_client(service)
 10. ows4R::WFSClient$new(...)
 11. ows4R (local) initialize(...)
     ...
 13. ows4R (local) initialize(...)
 14. private$fetchFeatureTypes(xmlObj, version)
 15. XML::getNodeSet(xmlObj, "//ns:FeatureType", wfsNs)
 17. XML:::xpathApply.XMLInternalDocument(...)
 18. XML::matchNamespaces(doc, namespaces)

[maelle]

@bart-v friendly reminder about my question above: what is the official URL of the chemistry contaminants WFS? Thanks in advance. 🙏