add matrix_synapse_oembed_additional_providers var

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

@@ -362,6 +362,9 @@ matrix_synapse_media_retention_local_media_lifetime:
 # should be empty to disable
 matrix_synapse_media_retention_remote_media_lifetime:
 
+# Controls the list of additional oembed providers to be added to the homeserver.
+matrix_synapse_oembed_additional_providers: []
+
 # The tmpfs at /tmp needs to be large enough to handle multiple concurrent file uploads.
 matrix_synapse_tmp_directory_size_mb: "{{ matrix_synapse_max_upload_size_mb * 50 }}"
 

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

@@ -1235,6 +1235,7 @@ oembed:
   #
   #additional_providers:
   #  - oembed/my_providers.json
+  additional_providers: {{ matrix_synapse_oembed_additional_providers|to_json }}
 
 
 ## Captcha ##