Recommendations on building new extension for crunchy containers

[jdenisgiguere]

** Which example are you working with? **

We are experimenting with some PostgreSQL extensions like https://github.com/dlr-eoc/pgh3.

What is the current behavior?

It's not very complicated for us to build extensions from source.
To integrate them on a crunchy container, it looks like the appropriate approach is to build an rpm of that extension.
We are not sure what would be the best strategy to build the rpm.

We can find general guidance for building rpm on centos (https://wiki.centos.org/HowTos/SetupRpmBuildEnvironment by example).

What is the expected behavior?

Do you have any recommendations regarding how to build a custom PostgreSQL extension RPM and integrate it into a crunchy container?

Other information (e.g. detailed explanation, related issues, etc)

This is related to issue #747 .

Please tell us about your environment:

We are willing to use any environment that would make this easier.