feat: add notification preferences database & audit support (#14100)

coderd/database/migrations/000238_notification_preferences.up.sql

@@ -0,0 +1,52 @@
+CREATE TABLE notification_preferences
+(
+	user_id                  uuid REFERENCES users ON DELETE CASCADE                  NOT NULL,
+	notification_template_id uuid REFERENCES notification_templates ON DELETE CASCADE NOT NULL,
+	disabled                 bool                                                     NOT NULL DEFAULT FALSE,
+	created_at               TIMESTAMP WITH TIME ZONE                                 NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	updated_at               TIMESTAMP WITH TIME ZONE                                 NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	PRIMARY KEY (user_id, notification_template_id)
+);
+
+-- Add a new type (to be expanded upon later) which specifies the kind of notification template.
+CREATE TYPE notification_template_kind AS ENUM (
+	'system'
+	);
+
+ALTER TABLE notification_templates
+	-- Allow per-template notification method (enterprise only).
+	ADD COLUMN method notification_method,
+	-- Update all existing notification templates to be system templates.
+	ADD COLUMN kind   notification_template_kind DEFAULT 'system'::notification_template_kind NOT NULL;
+COMMENT ON COLUMN notification_templates.method IS 'NULL defers to the deployment-level method';
+
+-- No equivalent in down migration because ENUM values cannot be deleted.
+ALTER TYPE notification_message_status ADD VALUE IF NOT EXISTS 'inhibited';
+
+-- Function to prevent enqueuing notifications unnecessarily.
+CREATE OR REPLACE FUNCTION inhibit_enqueue_if_disabled()
+	RETURNS TRIGGER AS
+$$
+BEGIN
+	-- Fail the insertion if the user has disabled this notification.
+	IF EXISTS (SELECT 1
+			   FROM notification_preferences
+			   WHERE disabled = TRUE
+				 AND user_id = NEW.user_id
+				 AND notification_template_id = NEW.notification_template_id) THEN
+		RAISE EXCEPTION 'cannot enqueue message: user has disabled this notification';
+	END IF;
+
+	RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Trigger to execute above function on insertion.
+CREATE TRIGGER inhibit_enqueue_if_disabled
+	BEFORE INSERT
+	ON notification_messages
+	FOR EACH ROW
+EXECUTE FUNCTION inhibit_enqueue_if_disabled();
+
+-- Allow modifications to notification templates to be audited.
+ALTER TYPE resource_type ADD VALUE IF NOT EXISTS 'notification_template';