feat(fleet): add support for url variable type

[andrewkroh]

Summary

Adds a new 'url' variable type to package policies, allowing for specific URL input and validation. This implements a feature that was added to package-spec 1.3.0 (Nov 16, 2021).

This change introduces validation for the URL format using the standard URL constructor and adds an optional 'url_allowed_schemes' property to restrict which URL schemes are permissible.

Relates: elastic/package-spec#241
Relates: #116914

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.

Screenshots

Release note

Adds support for a new url type variable in Fleet packages which provides better input validation of URLs in configurations.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[juliaElastic]

LGTM

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: d3edec3

Failed CI Steps

• Fleet Cypress Tests #2

Test Failures

• [job] [logs] Fleet Cypress Tests #2 / View agents list Agent status filter should filter on healthy and unhealthy
• [job] [logs] Fleet Cypress Tests #2 / View agents list Bulk actions should allow to bulk upgrade agents and cancel that upgrade

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
fleet	1464	1465	+1

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
fleet	171.9KB	172.5KB	+581.0B

Unknown metric groups

API count

id	before	after	diff
fleet	1596	1597	+1

History

• 💚 Build #327768 succeeded 7e9b830