Allow node_traits to define their own URLs

This extends our interpretation of dataset-supplied traits to allow them to define a URL as well as a value. If a url is specified, then the value (in the tip-clicked panel) is rendered as a link.

Closes #1307

src/components/tree/infoPanels/click.js

@@ -96,8 +96,7 @@ const MutationTable = ({mutations}) => {
 
 
 const AccessionAndUrl = ({node}) => {
-  const accession = getAccessionFromNode(node);
-  const url = getUrlFromNode(node);
+  const {accession, url} = getAccessionFromNode(node);
   const genbank_accession = getTraitFromNode(node, "genbank_accession");
 
   /* `gisaid_epi_isl` is a special value attached to nodes introduced during the 2019 nCoV outbreak.
@@ -230,10 +229,16 @@ const Trait = ({node, trait, colorings}) => {
       value = Number.parseFloat(value_tmp).toPrecision(3);
     }
   }
+  if (!isValueValid(value)) return null;
+
   const name = (colorings && colorings[trait] && colorings[trait].title) ?
     colorings[trait].title :
     trait;
-  return isValueValid(value) ? item(name, value) : null;
+  const url = getUrlFromNode(node, trait);
+  if (url) {
+    return <Link title={name} url={formatURL(url)} value={value}/>;
+  }
+  return item(name, value);
 };
 
 /**

src/util/treeMiscHelpers.js

@@ -69,15 +69,25 @@ export const getFullAuthorInfoFromNode = (node) =>
 
 export const getAccessionFromNode = (node) => {
   /* see comment at top of this file */
-  if (node.node_attrs && node.node_attrs.accession) {
-    return node.node_attrs.accession;
+  let accession, url;
+  if (node.node_attrs) {
+    if (isValueValid(node.node_attrs.accession)) {
+      accession = node.node_attrs.accession;
+    }
+    if (typeof node.node_attrs.url === "string") {
+      url = node.node_attrs.url;
+    }
   }
-  return undefined;
+  return {accession, url};
 };
 
 /* see comment at top of this file */
-export const getUrlFromNode = (node) =>
-  (node.node_attrs && node.node_attrs.url) ? node.node_attrs.url : undefined;
+export const getUrlFromNode = (node, trait) => {
+  if (node.node_attrs && node.node_attrs[trait] && typeof node.node_attrs[trait].url === "string") {
+    return node.node_attrs[trait].url;
+  }
+  return undefined;
+};
 
 /**
  * Traverses the tree and returns a set of genotype states such as