allow custom naming and/or recreate full dropdown for url-provided signals

[melange396]

Currently (or as of #36), url-provided base64-encoded signal specifications (as demonstrated with a link like this) show up with a single-line title of "value" in the LeftMenu component (before that changeset, the url-provided signals do not show up in the LeftMenu at all). The encoding includes a JSON dictionary with an entry for "title":"value", but changing the value for key "title" causes the signal to fail to load.

(ive only tested this with COVIDCast signals; behavior may be different for other endpoint sources)

[melange396]

a "normally" populated LeftMenu will look something like this:

[melange396]

#53 provided a huge improvement in the signal identifiers displayed in the epivis "legend".

We have an important use case requirement for replacing the default identifier/title/name strings with arbitrary, externally specified ones.

Enable this functionality by accepting a new optional field (called custom_title) in any signal entry found in the JSON structure that is encoded in sharable epivis URLs. When this field is present, the specified value should override the normal signal title (as constructed in

www-epivis/src/deriveLinkDefaults.ts

Lines 161 to 172 in 2ede365

	const col_name = d.title;
	d.title = `${d.params._endpoint}`;
	if (d.params.data_source && d.params.signal) {
	d.title += ` > ${d.params.data_source}:${d.params.signal}`;
	}
	if (d.params.geo_type && d.params.geo_value) {
	d.title += ` > ${d.params.geo_type}:${d.params.geo_value}`;
	}
	if (d.params.regions) {
	d.title += ` > ${d.params.regions}`;
	}
	d.title += ` > ${col_name}`;

).

[melange396]

#78 is merged now, which gives us the ability to specify custom titles via URL-encoded parameters, but i am going to leave this open for now in case we want to revisit creating the left-hand menu dropdowns of full sets of signals.