I need to add a /.well-known directory to my site with a JSON file in it, for an external service to verify that I own the domain.

I have tried adding a public/.well-known directory to my source repository, which does make the necessary file appear at the right location. However, this seems to be behind a 308 redirect, and the external service does not accept this as a valid HTTP response code. For example:

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curl -X HEAD -i 'https://[redacted].com/.well-known/microsoft-identity-association.json' 
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[...]
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HTTP/2 308 
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cache-control: public, max-age=0, must-revalidate
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content-type: text/plain
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date: Tue, 14 Jan 2025 18:57:40 GMT
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location: https://www.[redacted].com/.well-known/microsoft-identity-association.json
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refresh: 0;url=https://www.[redacted].com/.well-known/microsoft-identity-association.json
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server: Vercel
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strict-transport-security: max-age=63072000

And Microsoft's domain verification returns the following error message: "Verification of publisher domain failed. Request returned the wrong HTTP status code. Expected: OK, Actual: 308."

I tried searching the Vercel docs and got a recommendation to add the following to my vercel.json file, but this did not make any difference:

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    "routes": [
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        {
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            "src": "/.well-known/(.*)",
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            "dest": "public/.well-known/$1"
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        }
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    ]

How can I make a file appear in a /.well-known directory without any 308 redirect?