feat : added the author contact in the hierarchy for the contact sele…

[shahzan01]

Add Author Contact Fallback in Schema.org Plugin

Pull Request for Issue #<replace_with_issue_number>.

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Summary of Changes

This PR enhances the Schema.org system plugin with an improved contact fallback chain and configuration options.

New behavior (contact resolution order):

1. Manual fields – If a contact is explicitly set in the schema data for the role.
2. Selected contact – If a modal_contact is chosen in the schema form.
3. Author’s contact – If no contact is selected, the plugin now looks up the article’s created_by user and links to their preferred com_contact record.
   • If a user has multiple contact records, the plugin can be configured to map a specific user → contact in plugin parameters.
   • If no mapping exists, the first published contact for that user is used.
4. Default contact – Finally, if none of the above is available, the plugin uses the default contact defined in the plugin params.

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Testing Instructions

1. Go to Extensions → Plugins → System – Schema.org and configure:
   • A Default Contact.
   • (Optional) Add a mapping between authors and their preferred contacts.
2. Create or edit an article:
   • Case 1: Select a contact manually in the Schema tab → that contact appears in JSON-LD.
   • Case 2: Leave contact empty, ensure the author has a linked contact in com_contact → author’s contact appears in JSON-LD.
   • Case 3: Author has multiple contacts → the mapped contact in plugin params is used (or the first published contact if no mapping).
   • Case 4: No author contact → default contact appears.
3. Inspect the page source and verify the application/ld+json block contains