Add the ability to controll password-peppering for Synapse

Closes Github issue #5

roles/matrix-server/defaults/main.yml

@@ -68,6 +68,9 @@ matrix_synapse_rc_message_burst_count: 10.0
 # (things like number of users, number of messages sent, uptime, load, etc.)
 matrix_synapse_report_stats: false
 
+# Controls password-peppering for Matrix Synapse. Not to be changed after initial setup.
+matrix_synapse_password_config_pepper: ""
+
 # A list of additional "volumes" to mount in the container.
 # This list gets populated dynamically based on Synapse extensions that have been enabled.
 # Contains definition objects like this: `{"src": "/outside", "dst": "/inside", "options": "rw|ro|slave|.."}