How to set correct content-type for apple-app-site-association file on Nginx/Rails

Add in nginx:

location ~ /.well-known/apple-app-site-association {
         default_type application/pkcs7-mime;
 }

This worked for me within .htaccess:

<FilesMatch "apple-app-site-association">
    ForceType application/json
</FilesMatch>

It turns out the nginx configuration file described two servers, and I was adding the location snippet to the wrong one.

When I added it to the correct one and reloaded nginx, the file was returned with the expected content-type:

HTTP/1.1 200 OK
Server: nginx/1.10.1
Content-Type: application/pkcs7-mime
Content-Length: 245

{
"applinks": {
"apps": [],
"details": [
  {
    "appID": "APPPREFIX.com.mycompany.app",
    "paths": [
      "/home*"
    ]
  }
]

}