If you want to install Relevanssi Premium as a Composer package, you can use the following URL to fetch the latest version:
https://www.relevanssi.com/update/fetch_latest_version.php?api_key=XXX
Just replace XXX with your valid API key. The URL will always return the latest version of the plugin files. If you want a specific version, you can use
https://www.relevanssi.com/update/get_version.php?api_key=XXX&version=1.15.2.1
The Composer package should look something like this:
{
"type": "package",
"package": {
"name": "relevanssi/relevanssi-premium",
"version": "1.15.2.1",
"type": "wordpress-plugin",
"dist": {
"type": "zip",
"url": "https://www.relevanssi.com/update/get_version.php?api_key=XXX&version=1.15.2.1"
},
}
}