feat: implement thin vertical slice of system-generated notifications (#13537)

cli/testdata/coder_server_--help.golden

@@ -326,6 +326,30 @@ can safely ignore these settings.
           Minimum supported version of TLS. Accepted values are "tls10",
           "tls11", "tls12" or "tls13".
 
+NOTIFICATIONS OPTIONS: 
+      --notifications-dispatch-timeout duration, $CODER_NOTIFICATIONS_DISPATCH_TIMEOUT (default: 1m0s)
+          How long to wait while a notification is being sent before giving up.
+
+      --notifications-max-send-attempts int, $CODER_NOTIFICATIONS_MAX_SEND_ATTEMPTS (default: 5)
+          The upper limit of attempts to send a notification.
+
+      --notifications-method string, $CODER_NOTIFICATIONS_METHOD (default: smtp)
+          Which delivery method to use (available options: 'smtp', 'webhook').
+
+NOTIFICATIONS / EMAIL OPTIONS: 
+      --notifications-email-from string, $CODER_NOTIFICATIONS_EMAIL_FROM
+          The sender's address to use.
+
+      --notifications-email-hello string, $CODER_NOTIFICATIONS_EMAIL_HELLO (default: localhost)
+          The hostname identifying the SMTP server.
+
+      --notifications-email-smarthost host:port, $CODER_NOTIFICATIONS_EMAIL_SMARTHOST (default: localhost:587)
+          The intermediary SMTP host through which emails are sent.
+
+NOTIFICATIONS / WEBHOOK OPTIONS: 
+      --notifications-webhook-endpoint url, $CODER_NOTIFICATIONS_WEBHOOK_ENDPOINT
+          The endpoint to which to send webhooks.
+
 OAUTH2 / GITHUB OPTIONS: 
       --oauth2-github-allow-everyone bool, $CODER_OAUTH2_GITHUB_ALLOW_EVERYONE
           Allow all logins, setting this option means allowed orgs and teams

cli/testdata/server-config.yaml.golden

@@ -493,3 +493,58 @@ userQuietHoursSchedule:
 # compatibility reasons, this will be removed in a future release.
 # (default: false, type: bool)
 allowWorkspaceRenames: false
+notifications:
+  # Which delivery method to use (available options: 'smtp', 'webhook').
+  # (default: smtp, type: string)
+  method: smtp
+  # How long to wait while a notification is being sent before giving up.
+  # (default: 1m0s, type: duration)
+  dispatch-timeout: 1m0s
+  email:
+    # The sender's address to use.
+    # (default: <unset>, type: string)
+    from: ""
+    # The intermediary SMTP host through which emails are sent.
+    # (default: localhost:587, type: host:port)
+    smarthost: localhost:587
+    # The hostname identifying the SMTP server.
+    # (default: localhost, type: string)
+    hello: localhost
+  webhook:
+    # The endpoint to which to send webhooks.
+    # (default: <unset>, type: url)
+    hello:
+  # The upper limit of attempts to send a notification.
+  # (default: 5, type: int)
+  max-send-attempts: 5
+  # The minimum time between retries.
+  # (default: 5m0s, type: duration)
+  retry-interval: 5m0s
+  # The notifications system buffers message updates in memory to ease pressure on
+  # the database. This option controls how often it synchronizes its state with the
+  # database. The shorter this value the lower the change of state inconsistency in
+  # a non-graceful shutdown - but it also increases load on the database. It is
+  # recommended to keep this option at its default value.
+  # (default: 2s, type: duration)
+  store-sync-interval: 2s
+  # The notifications system buffers message updates in memory to ease pressure on
+  # the database. This option controls how many updates are kept in memory. The
+  # lower this value the lower the change of state inconsistency in a non-graceful
+  # shutdown - but it also increases load on the database. It is recommended to keep
+  # this option at its default value.
+  # (default: 50, type: int)
+  store-sync-buffer-size: 50
+  # How long a notifier should lease a message. This is effectively how long a
+  # notification is 'owned' by a notifier, and once this period expires it will be
+  # available for lease by another notifier. Leasing is important in order for
+  # multiple running notifiers to not pick the same messages to deliver
+  # concurrently. This lease period will only expire if a notifier shuts down
+  # ungracefully; a dispatch of the notification releases the lease.
+  # (default: 2m0s, type: duration)
+  lease-period: 2m0s
+  # How many notifications a notifier should lease per fetch interval.
+  # (default: 20, type: int)
+  lease-count: 20
+  # How often to query the database for queued notifications.
+  # (default: 15s, type: duration)
+  fetch-interval: 15s