how to upgrade postgresql?

[Stuart McGraw]

I am not sure if this is a Ubuntu question or a Postgresql one
but I have to start somewhere so...

I am new to Ubuntu and have installed 17.10.  17.10 comes with
Postgresql-9.6.6 by default but I have requirement for Postgresql-10
so I did not install postgresql from Ubuntu's repos but instead
added this file to /etc/apt/sources.list.d/:

   deb http://apt.postgresql.org/pub/repos/apt/ zesty-pgdg main

The pgdg repo does not apparently provides a separate package
for artful (17.10), one is supposed to use the zesty package[*1].
I eventually got it installed, working around a version conflict
with a perl package (libdbd-pg-perl).

However, when I did this several months ago, the current pg
version was 10.1.  It is now 10.3 but despite doing a "apt-get
update; apt-get upgrade" (or dist-upgrade) apt does not offer
to upgrade postgresql.  When I do "apt list 'postgresql-*" I
see only postgresql-10.1 packages.

Since I am new to Ubuntu I am kind of lost as to how to figure
out what is wrong and get postgresql upgraded.  Any suggestions?

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[*1] https://dba.stackexchange.com/questions/190845/postgresql-10-for-ubuntu-17-10-artful