Fix Bug 53170 / Add the ability to set secure_link_secret (#444)

* Add securelink generation

* Add ability to configure securelink_secret

* Add a description of SECURE_LINK_SECRET

* Update README.md

README.md

@@ -187,6 +187,7 @@ Below is the complete list of parameters that can be set using environment varia
 - **REDIS_SERVER_PORT**:  The Redis server port number.
 - **NGINX_WORKER_PROCESSES**: Defines the number of nginx worker processes.
 - **NGINX_WORKER_CONNECTIONS**: Sets the maximum number of simultaneous connections that can be opened by a nginx worker process.
+- **SECURE_LINK_SECRET**: Defines secret for the nginx config directive [secure_link_md5](http://nginx.org/ru/docs/http/ngx_http_secure_link_module.html#secure_link_md5). Defaults to `random string`.
 - **JWT_ENABLED**: Specifies the enabling the JSON Web Token validation by the ONLYOFFICE Document Server. Defaults to `false`.
 - **JWT_SECRET**: Defines the secret key to validate the JSON Web Token in the request to the ONLYOFFICE Document Server. Defaults to `secret`.
 - **JWT_HEADER**: Defines the http header that will be used to send the JSON Web Token. Defaults to `Authorization`.

run-document-server.sh

@@ -468,6 +468,8 @@ update_nginx_settings(){
   if [ -f "${NGINX_ONLYOFFICE_EXAMPLE_CONF}" ]; then
     sed 's/linux/docker/' -i ${NGINX_ONLYOFFICE_EXAMPLE_CONF}
   fi
+
+  documentserver-update-securelink.sh -s ${SECURE_LINK_SECRET:-$(pwgen -s 20)}
 }
 
 update_supervisor_settings(){