Deprecate matrix_synapse_account_threepid_delegates_email before Synapse v1.66.0

This is done in anticipation of this option's removal in the
upcoming Synapse v1.66.0 release (likely tomorrow).

See: https://matrix-org.github.io/synapse/v1.66/upgrade.html#delegation-of-email-validation-no-longer-supported

roles/matrix-synapse/defaults/main.yml

@@ -257,10 +257,6 @@ matrix_synapse_registrations_require_3pid: []
 #    pattern: '\+44'
 matrix_synapse_allowed_local_3pids: []
 
-# The server to use for email threepid validation. When empty, Synapse does it by itself.
-# Otherwise, this should be pointed to an identity server.
-matrix_synapse_account_threepid_delegates_email: ''
-
 # The server to use for phone number threepid validation. When empty, validation cannot happen, as Synapse doesn't support it.
 # To make it work, this should be pointed to an identity server.
 matrix_synapse_account_threepid_delegates_msisdn: ''

roles/matrix-synapse/tasks/validate_config.yml

@@ -61,6 +61,7 @@
     - {'old': 'matrix_synapse_use_presence', 'new': 'matrix_synapse_presence_enabled'}
     - {'old': 'matrix_synapse_version_arm64', 'new': '<superseded by matrix_synapse_version - see https://github.com/matrix-org/synapse/pull/11810>'}
     - {'old': 'matrix_synapse_enable_group_creation', 'new': '<removed in Synapse v1.61.0 - use the new Spaces feature instead>'}
+    - {'old': 'matrix_synapse_account_threepid_delegates_email', 'new': '<removed in Synapse v1.66.0 - make sure to configure email settings for Synapse - see https://matrix-org.github.io/synapse/v1.66/upgrade.html#delegation-of-email-validation-no-longer-supported>'}
 
 - name: (Deprecation) Catch and report renamed settings in matrix_synapse_configuration_extension_yaml
   ansible.builtin.fail:

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

@@ -1419,14 +1419,10 @@ allow_guest_access: {{ matrix_synapse_allow_guest_access|to_json }}
 #
 #default_identity_server: https://matrix.org
 
-# Handle threepid (email/phone etc) registration and password resets through a set of
+# Handle threepid (phone etc) registration and password resets through a set of
 # *trusted* identity servers. Note that this allows the configured identity server to
 # reset passwords for accounts!
 #
-# Be aware that if `email` is not set, and SMTP options have not been
-# configured in the email config block, registration and user password resets via
-# email will be globally disabled.
-#
 # Additionally, if `msisdn` is not set, registration and password resets via msisdn
 # will be disabled regardless, and users will not be able to associate an msisdn
 # identifier to their account. This is due to Synapse currently not supporting
@@ -1441,7 +1437,6 @@ allow_guest_access: {{ matrix_synapse_allow_guest_access|to_json }}
 # https://matrix.org/docs/spec/identity_service/latest
 #
 account_threepid_delegates:
-    email: {{ matrix_synapse_account_threepid_delegates_email|to_json }}
     msisdn: {{ matrix_synapse_account_threepid_delegates_msisdn|to_json }}
 
 # Whether users are allowed to change their displayname after it has