Build v10 header component. Amend LinkViewModel to allow for nullable inputs.

[akdalin-hee]

Description

Build v10 header component. Amend LinkViewModel to allow for nullable inputs.

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Developer checks

(Leave tasks unticked if they haven't been appropriate for your ticket.)

I have:

• Run the IDE auto formatter on all files I’ve worked on and made sure there are no IDE errors relating to them
• Written or updated tests for the changes and made sure all tests are passing
• Manually tested my work with and without JavaScript (adding notes where functionality requires JavaScript)
• Tested with Wave Chrome plugin. Addressed any valid accessibility issues and documented any invalid errors
• Scanned over my pull request in GitHub and addressed any warnings from the GitHub Build and Test checks in the GitHub PR ‘Files Changed’ tab
  Either:
• Documented my work in Confluence, updating any business rules applied or modified. Updated GitHub readme/documentation for the repository if appropriate. List of documentation links added/changed:
  • doc_1_here
    Or:
• Confirmed that none of the work that I have undertaken requires any updates to documentation
• CHANGELOG entry