Allow pg_createsubscriber to reuse existing publications instead of failing when they already exist on the publisher. Previously, pg_createsubscriber would fail if any specified publication already existed. Now, existing publications are reused as-is with their current configuration, and non-existing publications are created automatically with FOR ALL TABLES. This change provides flexibility when working with mixed scenarios of existing and new publications. Users should verify that existing publications have the desired configuration before reusing them, and can use --dry-run with verbose mode to see which publications will be reused and which will be created. Only publications created by pg_createsubscriber are cleaned up during error cleanup operations. Pre-existing publications are preserved unless '--clean=publications' is explicitly specified, which drops all publications. This feature would be helpful for pub-sub configurations where users want to subscribe to a subset of tables from the publisher. Author: Shubham Khanna <khannashubham1197@gmail.com> Reviewed-by: Euler Taveira <euler@eulerto.com> Reviewed-by: Peter Smith <smithpb2250@gmail.com> Reviewed-by: Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: vignesh C <vignesh21@gmail.com> Reviewed-by: tianbing <tian_bing_0531@163.com> Discussion: https://postgr.es/m/CAHv8Rj%2BsxWutv10WiDEAPZnygaCbuY2RqiLMj2aRMH-H3iZwyA%40mail.gmail.com