synapse - introduce matrix_synapse_url_preview_url_blacklist var

roles/custom/matrix-synapse/defaults/main.yml

@@ -823,6 +823,11 @@ matrix_synapse_url_preview_ip_range_blacklist:
 # List of IP address CIDR ranges that the URL preview spider is allowed to access even if they are specified in `matrix_synapse_url_preview_ip_range_blacklist`.
 matrix_synapse_url_preview_ip_range_whitelist: []
 
+# List of URL matches that the URL preview spider is denied from accessing.
+# See https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#url_preview_url_blacklist
+# for more details.
+matrix_synapse_url_preview_url_blacklist: []
+
 # A list of values for the Accept-Language HTTP header used when downloading webpages during URL preview generation
 matrix_url_preview_accept_language: ['en-US', 'en']
 

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

@@ -1161,7 +1161,10 @@ url_preview_ip_range_whitelist: {{ matrix_synapse_url_preview_ip_range_whitelist
 # specified component matches for a given list item succeed, the URL is
 # blacklisted.
 #
-#url_preview_url_blacklist:
+{% if matrix_synapse_url_preview_url_blacklist | length > 0 %}
+url_preview_url_blacklist: {{ matrix_synapse_url_preview_url_blacklist | to_json }}
+{% endif %}
+
 #  # blacklist any URL with a username in its URI
 #  - username: '*'
 #