feat: add author filter command to template filtering (#19202)

Can do `author:username` to filter templates created by a certain
author. Adding to help clean out some templates that I created on our
dev instance. This makes sorting a bit easier.

coderd/database/queries/templates.sql

@@ -59,6 +59,19 @@ WHERE
 			tv.has_ai_task = sqlc.narg('has_ai_task') :: boolean
 		ELSE true
 	END
+	-- Filter by author_id
+	AND CASE
+		  WHEN @author_id :: uuid != '00000000-0000-0000-0000-000000000000'::uuid THEN
+			  t.created_by = @author_id
+		  ELSE true
+	END
+	-- Filter by author_username
+	AND CASE
+		  WHEN @author_username :: text != '' THEN
+			  t.created_by = (SELECT id FROM users WHERE lower(users.username) = lower(@author_username) AND deleted = false)
+		  ELSE true
+	END
+
   -- Authorize Filter clause will be injected below in GetAuthorizedTemplates
   -- @authorize_filter
 ORDER BY (t.name, t.id) ASC