Adding support for email links in a URL template for fields in Discover

[JessicaGarson]

A community Slack user is looking to format a field in the URL template to direct to an email link like mailto:youremail.com.

They tried adding mailto:{{value}} to the URL template, but it redirects to a link like https://my-deployment-kb.us-east-2.aws.found.io:93/app/mailto:e25%40yahoo.com. I think this is because we only support links that start with https:// .

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

Has been asked before: #16983 (comment)

[kertal]

Currently whitelisted URL Schemas can be found here:

kibana/src/core_plugins/kibana/common/field_formats/types/url.js

Line 5 in d06ee13

const whitelistUrlSchemes = ['http://', 'https://'];

On the surface it seems to be a low hanging fruit to add mailto:

[ghudgins]

addressed in #200070