This allows for a more graceful error message for the case of users who need to update their volume path.
I tested this with 17 and `--env PGDATA=/var/lib/postgresql/17/docker` (to make sure it still works fine and doesn't complain about the extra volume provided by Docker/`VOLUME`) and 18 with `-v /var/lib/postgresql/data` (where it appropriately errors and explains to me what I should be doing instead).
I also did a reflow on some text in the error message that's designed to fit in 80 columns but was taking 81. 😂
This is a bit complicated to use in Docker (because `io_uring` has a long and storied security story), but it is a new feature of 18+ that we should probably explicitly support for users who want to jump through the hoops to use it despite the security risk.
Additionally, this re-alphabetizes our `--with-xxx` flags.
When we added these lines, we needed newer files than PostgreSQL had upstream, but the situation has changed and we were pinned to a specific commit from 2017 - the _oldest_ PostgreSQL release version has a file from 2020.
* Unset NOTIFY_SOCKET when running the temporary server.
Postgres has native support for this notification socket and will write a `READY=1` message once it is ready and accepting connections. Unfortunately, the temporary server used by the `docker-entrypoint.sh` also sends a message on the socket, making it appear as though the container is ready and serving connections when it is not.
* Remove inaccurate references to corruption, remove SEGTERM suggestion, update information links to current docs. Postgres is carefully designed such that data is not corrupted on crashes or unclean shutdowns - the main tradeoff is that WAL replay is needed on startup. In practice, SIGTERM can cause unexpected long delays to shutdowns - often during maintenance windows - so best not to actively suggest this. The links back to official Postgres documentation seem sufficient.
There's a major issue with `su-exec` whose fix has gone unreleased for 5 years (typos leading to running code as root, the opposite of the purpose of the program).
This also decreases our Debian vs Alpine variance.
Due to user scripts/downstream code potentially using `su-exec`, I have included a compatibility symlink to `su-exec` for all versions less than the 17 pre-release.
