Add properties to middleware crd headers

[iameskild]

Fixes | Closes | Resolves #

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Changes introduced in this PR:

• Add the ability to add headers to traefik middleware

Types of changes

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
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Testing

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Documentation

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• Yes, docstrings
• Yes, main documentation
• Yes, deprecation notices

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