Kazunori Kimura 260f548c5b Ship with multiple versions of postgresql-client
It is intended to work even in environments without an internet connection.

- Use latest version of pg_isready on checking database connection
- Switch postgresql-client version checking server on startup
- If the server versions do not match exactly, use the latest installed client
  and warn on docker log

From postgresql documentation:
https://www.postgresql.org/docs/15/app-pgdump.html#PG-DUMP-NOTES

> Also, it is not guaranteed that pg_dump's output can be loaded
> into a server of an older major version — not even if the dump
> was taken from a server of that version.

To switch client version, generate a file ~/.postgresqlrc with content like:

{server side major version} {server hostname}:{server port} {default database}

See detail on:
https://manpages.ubuntu.com/manpages/bionic/man5/postgresqlrc.5.html

Following messages appear on docker log:

- Detected server version: 140007
- Generating /home/git/.postgresqlrc
2023-05-12 06:58:11 +09:00
..