Derive custom titles from URL params

[rzats]

See #42 (comment):

Accepts 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.

[rzats]

URL for testing:

https://deploy-preview-78--cmu-delphi-epivis.netlify.app/#eyJjaGFydCI6eyJ2aWV3cG9ydCI6WzcyOTI5Ni41LC0wLjg3NTMyMjQ2MjcwOTk1NDUsNzM5MjA5LjUsOC45NDIzMDU4MzQ3MDg2NzhdLCJzaG93UG9pbnRzIjpmYWxzZX0sImRhdGFzZXRzIjpbeyJjb2xvciI6IiM0ZGIxMmUiLCJ0aXRsZSI6IiV3SUxJIiwicGFyYW1zIjp7Il9lbmRwb2ludCI6ImZsdXZpZXciLCJyZWdpb25zIjoibmF0IiwgImN1c3RvbV90aXRsZSI6IkN1c3RvbSBUaXRsZSBIZXJlIn19XX0=

This represents the following JSON:

{"chart":{"viewport":[729296.5,-0.8753224627099545,739209.5,8.942305834708678],"showPoints":false},"datasets":[{"color":"#4db12e","title":"%wILI","params":{"_endpoint":"fluview","regions":"nat", "custom_title":"Custom Title Here"}}]}

[melange396]

Theres an issue with this: with two covidcast signals, a title is being overwritten...

this url:
https://deploy-preview-78--cmu-delphi-epivis.netlify.app/#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
with a payload that decodes to:
{"chart":{"viewport":[737451.5,-1471,739209.5,14529],"showPoints":false},"datasets":[{"color":"#39aa9c","title":"value","params":{"custom_title":"ABCD","_endpoint":"covidcast","data_source":"nchs-mortality","signal":"deaths_allcause_incidence_num","time_type":"week","geo_type":"state","geo_value":"ny"}},{"color":"#434d6b","title":"value","params":{"_endpoint":"covidcast","data_source":"nchs-mortality","signal":"deaths_allcause_incidence_num","time_type":"week","geo_type":"state","geo_value":"pa","custom_title":"EFGH"}}]}
that represents two entries of the same signal, identical except for geo_value and custom_title, shows up with the same custom title for each ("EFGH"):

it also happens without custom titles specified; note that both show up with the same state in the title using the netlify preview url for this PR, but are differentiated on production epivis (with the same payload).

[melange396]

• i have some exploration and ideas in testing custom_title handling #79 that should be useful for you

[melange396]

this works!