Fixes #5833, Fixes #5835 metatag keywords, source domain.

[tadean]

Description

This PR adds a dedicated source domain to the index, and includes the metatag keywords, both as the existing values and as versions transformed to hyphenated tags.

Release notes

`az_search_api` will now index the site's XMLsitemap domain, and metatag keywords.

Related issues

#5833
#5835

How to test

• Complete secrets setup or deploy to pantheon as explained in Fixes #5600 az_search_api document extraction #5610
• Create some page content.
  • include metatag keywords.
    • Include a single word
    • Include content keywords that are a delimited list
  • Ensure the site has an xmlsitemap base domain set
• enable az_search_api
• visit /admin/config/search/search-api/index/az_search_api_index
• click index now
• Wait for documents to be indexed ( can take several minutes to commit and be visible in the cluster)
• Examine documents in the index
• Verify ss_source_domain contains the base xml site domain
• Verify tm_X3b_en_keywords contains the keywords split on comma delimiters
• Verify sm_keyword_tags contains the lowercase keywords with whitespace turned into hyphens

Types of changes

Arizona Quickstart (install profile, custom modules, custom theme)

• Patch release changes
  • Bug fix
  • Accessibility, performance, or security improvement
  • Critical institutional link or brand change
  • Adding experimental module
  • Update experimental module
• Minor release changes
  • New feature
  • Breaking or visual change to existing behavior
  • Upgrade experimental module to stable
  • Enable existing module by default or database update
  • Non-critical brand change
  • New internal API or API improvement with backwards compatibility
  • Risky or disruptive cleanup to comply with coding standards
  • High-risk or disruptive change (requires upgrade path, risks regression, etc.)
• Other or unknown
  • Other or unknown

Drupal core

• Patch release changes
  • Security update
  • Patch level release (non-security bug-fix release)
  • Patch removal that's no longer necessary
• Minor release changes
  • Major or minor level update
• Other or unknown
  • Other or unknown

Drupal contrib projects

• Patch release changes
  • Security update
  • Patch or minor level update
  • Add new module
  • Patch removal that's no longer necessary
• Minor release changes
  • Major level update
• Other or unknown
  • Other or unknown

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My change requires release notes.