Add variable to disable homeserver url preview

roles/matrix-synapse/defaults/main.yml

@@ -167,6 +167,10 @@ matrix_synapse_password_providers_enabled: false
 # to load message content directly from the homeserver.
 matrix_synapse_push_include_content: true
 
+# If url previews should be generated. This will cause a request from Synapse to
+# URLs shared by users.
+matrix_synapse_url_preview_enabled: true
+
 # Enable exposure of metrics to Prometheus
 # See https://github.com/matrix-org/synapse/blob/master/docs/metrics-howto.rst
 matrix_synapse_metrics_enabled: false

roles/matrix-synapse/templates/synapse/homeserver.yaml.j2

@@ -525,7 +525,7 @@ max_upload_size: "{{ matrix_synapse_max_upload_size_mb }}M"
 # an explicit url_preview_ip_range_blacklist of IPs that the spider is
 # denied from accessing.
 #
-url_preview_enabled: true
+url_preview_enabled: {{ matrix_synapse_url_preview_enabled|to_json }}
 
 # List of IP address CIDR ranges that the URL preview spider is denied
 # from accessing.  There are no defaults: you must explicitly
@@ -1169,4 +1169,4 @@ alias_creation_rules: {{ matrix_alias_creation_rules|to_json }}
 #    room_id: "*"
 #    action: allow
 
-room_list_publication_rules: {{ matrix_room_list_publication_rules|to_json }}
+room_list_publication_rules: {{ matrix_room_list_publication_rules|to_json }}