feat: allow notification templates to be disabled by default (#16093)

Change as part of https://github.com/coder/coder/pull/16071

It has been decided that we want to be able to have some notification
templates be disabled _by default_
https://github.com/coder/coder/pull/16071#issuecomment-2580757061.

This adds a new column (`enabled_by_default`) to
`notification_templates` that defaults to `TRUE`. It also modifies the
`inhibit_enqueue_if_disabled` function to reject notifications for
templates that have `enabled_by_default = FALSE` with the user not
explicitly enabling it.

coderd/database/migrations/000284_allow_disabling_notification_templates_by_default.down.sql

@@ -0,0 +1,18 @@
+ALTER TABLE notification_templates DROP COLUMN enabled_by_default;
+
+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;

coderd/database/migrations/000284_allow_disabling_notification_templates_by_default.up.sql

@@ -0,0 +1,29 @@
+ALTER TABLE notification_templates ADD COLUMN enabled_by_default boolean DEFAULT TRUE NOT NULL;
+
+CREATE OR REPLACE FUNCTION inhibit_enqueue_if_disabled()
+	RETURNS TRIGGER AS
+$$
+BEGIN
+	-- Fail the insertion if one of the following:
+	--  * the user has disabled this notification.
+	--  * the notification template is disabled by default and hasn't
+	--    been explicitly enabled by the user.
+	IF EXISTS (
+		SELECT 1 FROM notification_templates
+		LEFT JOIN notification_preferences
+			ON  notification_preferences.notification_template_id = notification_templates.id
+			AND notification_preferences.user_id = NEW.user_id
+		WHERE notification_templates.id = NEW.notification_template_id AND (
+			-- Case 1: The user has explicitly disabled this template
+			notification_preferences.disabled = TRUE
+			OR
+			-- Case 2: The template is disabled by default AND the user hasn't enabled it
+			(notification_templates.enabled_by_default = FALSE AND notification_preferences.notification_template_id IS NULL)
+		)
+	) THEN
+		RAISE EXCEPTION 'cannot enqueue message: notification is not enabled';
+	END IF;
+
+	RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;

coderd/database/migrations/000285_disable_workspace_created_and_manually_updated_notifications_by_default.down.sql

@@ -0,0 +1,9 @@
+-- Enable 'workspace created' notification by default
+UPDATE notification_templates
+SET enabled_by_default = TRUE
+WHERE id = '281fdf73-c6d6-4cbb-8ff5-888baf8a2fff';
+
+-- Enable 'workspace manually updated' notification by default
+UPDATE notification_templates
+SET enabled_by_default = TRUE
+WHERE id = 'd089fe7b-d5c5-4c0c-aaf5-689859f7d392';

coderd/database/migrations/000285_disable_workspace_created_and_manually_updated_notifications_by_default.up.sql

@@ -0,0 +1,9 @@
+-- Disable 'workspace created' notification by default
+UPDATE notification_templates
+SET enabled_by_default = FALSE
+WHERE id = '281fdf73-c6d6-4cbb-8ff5-888baf8a2fff';
+
+-- Disable 'workspace manually updated' notification by default
+UPDATE notification_templates
+SET enabled_by_default = FALSE
+WHERE id = 'd089fe7b-d5c5-4c0c-aaf5-689859f7d392';