use docker secrets for bbb

.env.sample

@@ -14,7 +14,8 @@ ADMIN_USER=admin
 SECRET_DB_ROOT_PASSWORD_VERSION=v1
 SECRET_DB_PASSWORD_VERSION=v1
 SECRET_ADMIN_PASSWORD_VERSION=v1
-# SECRET_ONLYOFFICE_JWT_VERSION=v1
+SECRET_ONLYOFFICE_JWT_VERSION=v1
+SECRET_BBB_SECRET_VERSION=v1
 
 EXTRA_VOLUME=/dev/null:/tmp/.dummy
 
@@ -22,3 +23,4 @@ EXTRA_VOLUME=/dev/null:/tmp/.dummy
 # X_FRAME_OPTIONS_ALLOW_FROM=embedding-site.example.org
 # APPS="calendar sociallogin onlyoffice"
 # ONLYOFFICE_URL=https://onlyoffice.example.com
+# BBB_URL=https://talk.example.org/bigbluebutton/ # trailing slash!