Add dynamic TURN configuration in the Docker image

contrib/docker/README.md

@@ -87,9 +87,12 @@ Synapse specific settings:
 * ``SYNAPSE_REPORT_STATS``, set this variable to `yes` to enable anonymous
   statistics reporting back to the Matrix project which helps us to get funding.
 * ``SYNAPSE_RECAPTCHA_PUBLIC_KEY``, set this variable to the recaptcha public
-  key in order to enable recaptcha upon registration
+  key in order to enable recaptcha upon registration.
 * ``SYNAPSE_RECAPTCHA_PRIVATE_KEY``, set this variable to the recaptcha private
-  key in order to enable recaptcha upon registration
+  key in order to enable recaptcha upon registration.
+* ``SYNAPSE_TURN_URIS``, set this variable to the coma-separated list of TURN
+  uris to enable TURN for this homeserver.
+* ``SYNAPSE_TURN_SECRET``, set this to the TURN shared secret if required.
 
 Shared secrets, these will be initialized to random values if not set:
 

contrib/docker/conf/homeserver.yaml

@@ -126,10 +126,19 @@ recaptcha_siteverify_api: "https://www.google.com/recaptcha/api/siteverify"
 
 ## Turn ##
 
+{% if SYNAPSE_TURN_URIS %}
+turn_uris:
+{% for uri in SYNAPSE_TURN_URIS.split(',') %}  - {{ uri }}
+{% endfor %}
+turn_shared_secret: "{{ SYNAPSE_TURN_SECRET }}"
+turn_user_lifetime: "1h"
+turn_allow_guests: True
+{% else %}
 turn_uris: []
 turn_shared_secret: "YOUR_SHARED_SECRET"
 turn_user_lifetime: "1h"
 turn_allow_guests: True
+{% endif %}
 
 ## Registration ##