Merge pull request #3335 from Poulpatine/hedgedoc_integration

allow hedgedoc integration

src/server/routes/hackmd.js

@@ -191,8 +191,8 @@ module.exports = function(crowi, app) {
 
     const { status, headers } = hackmdResponse;
 
-    // validate HackMD/CodiMD specific header
-    if (headers['codimd-version'] == null && headers['hackmd-version'] == null) {
+    // validate HackMD/CodiMD/HedgeDoc specific header
+    if (headers['codimd-version'] == null && headers['hackmd-version'] == null && headers['hedgedoc-version'] == null) {
       const message = 'Connecting to a non-HackMD server.';
       logger.error(message);
       return res.json(ApiResponse.error(message));