chore: add template_with_user view to include user contextual data (#8568)

* chore: Refactor template sql queries to use new view
* TemplateWithUser -> Template
* Add unit test to enforce good view

coderd/database/migrations/000138_join_users.down.sql

@@ -0,0 +1,6 @@
+BEGIN;
+
+DROP VIEW template_with_users;
+DROP VIEW visible_users;
+
+COMMIT;

coderd/database/migrations/000138_join_users.up.sql

@@ -0,0 +1,30 @@
+BEGIN;
+
+CREATE VIEW
+	visible_users
+AS
+SELECT
+	id, username, avatar_url
+FROM
+	users;
+
+COMMENT ON VIEW visible_users IS 'Visible fields of users are allowed to be joined with other tables for including context of other resources.';
+
+-- If you need to update this view, put 'DROP VIEW template_with_users;' before this.
+CREATE VIEW
+    template_with_users
+AS
+    SELECT
+        templates.*,
+		coalesce(visible_users.avatar_url, '') AS created_by_avatar_url,
+		coalesce(visible_users.username, '') AS created_by_username
+    FROM
+        templates
+    LEFT JOIN
+		visible_users
+	ON
+	    templates.created_by = visible_users.id;
+
+COMMENT ON VIEW template_with_users IS 'Joins in the username + avatar url of the created by user.';
+
+COMMIT;