add LDAP method as environment variable

config/initializers/omniauth.rb

@@ -13,7 +13,7 @@ Rails.application.config.middleware.use OmniAuth::Builder do
   provider :ldap,
     host: ENV['LDAP_SERVER'],
     port: ENV['LDAP_PORT'],
-    method: :plain,
+    method: ENV['LDAP_METHOD'].present? ? ENV['LDAP_METHOD'].to_sym : :plain,
     allow_username_or_email_login: true,
     uid: ENV['LDAP_UID'],
     base: ENV['LDAP_BASE'],

env

@@ -38,12 +38,13 @@ GOOGLE_OAUTH2_SECRET=
 
 # LDAP Login Provider (optional)
 #
-#   You can enable LDAP authentication by providing values for LDAP_SERVER and LDAP_PORT.
+#   You can enable LDAP authentication by providing values for the variables below.
 #   For information about setting up LDAP, see: 
 #     http://docs.bigbluebutton.org/install/green-light.html#ldap-oauth
 #
 LDAP_SERVER=
 LDAP_PORT=
+LDAP_METHOD=
 LDAP_UID=
 LDAP_BASE=
 LDAP_BIND_DN=