make nameserver configurable

config.yaml

@@ -2,7 +2,9 @@ authority:
   jwks: ./jwks.json
   base_url: 'https://api.rd.nic.fr/id4me/authority'
   listen: '127.0.0.1:8078'
-  database_url: 'postgres://aim-api:aim-api@localhost:5432/aim-api'
+  database_url: 'postgres://id4me:id4me@localhost:5432/id4me'
   # Cookie encryption keys, in descending order of freshness
   cookie_keys:
     - change-me
+  # optional, list of DNS resolvers to use in host[:port] formart
+  #nameservers: []

src/adapter.js

@@ -3,7 +3,7 @@
 
 const Sequelize = require('sequelize'); // eslint-disable-line import/no-unresolved
 
-const { database_url } = require('./config')
+const { database_url } = require('./config');
 const sequelize = new Sequelize(database_url);
 
 const grantable = new Set([

src/id4me.js

-const dns = require('dns');
+const { Resolver } = require('dns');
+const { nameservers } = require('./config');
+
+const resolver = new Resolver();
+
+if (nameservers && nameservers.length > 0) {
+  resolver.setServers(nameservers);
+}
 
 function getOidcConfigFromDns(identifier) {
   // TODO: identifier can be email
@@ -25,7 +32,7 @@ function getOidcConfigFromDns(identifier) {
 
 function lookupOidcTxt(oidcDomain) {
   return new Promise( (resolve, reject) => {
-    dns.resolve(`_oidc.${oidcDomain}`, 'TXT', (err, data) => {
+    resolver.resolve(`_oidc.${oidcDomain}`, 'TXT', (err, data) => {
       if (err) {
         return reject(err)
       }