Add matrix_synapse_url_preview_url_blacklist var (#4641)

* synapse - introduce matrix_synapse_url_preview_url_blacklist var

* Preserve original comments around `url_preview_url_blacklist`

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Co-authored-by: Aleksandrs Jansons <alex@peledu.casa>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

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

@@ -1178,6 +1178,9 @@ url_preview_ip_range_whitelist: {{ matrix_synapse_url_preview_ip_range_whitelist
 #
 #  # blacklist any URL with a literal IPv4 address
 #  - netloc: '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$'
+{% if matrix_synapse_url_preview_url_blacklist | length > 0 %}
+url_preview_url_blacklist: {{ matrix_synapse_url_preview_url_blacklist | to_json }}
+{% endif %}
 
 # The largest allowed URL preview spidering size in bytes
 #