Switch to the official oidc issuer link rel value

Author: dmitrizagidulin

lib/handlers/options.js

@@ -17,7 +17,7 @@ function linkAuthProvider (req, res) {
   let locals = req.app.locals
   if (locals.authMethod === 'oidc') {
     let oidcProviderUri = locals.host.serverUri
-    addLink(res, oidcProviderUri, 'oidc.provider')
+    addLink(res, oidcProviderUri, 'http://openid.net/specs/connect/1.0/issuer')
   }
 }