Make inclusion of schema 'public' in search_path configurable

Since version 1.6.0 of the Postgres Operator the public schema is not part of the search_path of default users of a prepared database (also see issue #1129). This change of behaviour causes trouble when using the postgis extension. Many 3rd party applications assume that the functions are installed in a schema that is part of the search path (usually public) and don't use the fully qualified name.

A work-around is to set the search_path using an SQL query, but that means that we have to use an extended Spilo image. I'd like to propose to make the inclusion of the public schema configurable via the Custom Resource Definition so that the user can decide for each cluster whether it is necessary to expand the search_path of the default users or not.

Please, answer some short questions which should help us to understand your problem / question better?

• Which image of the operator are you using? registry.opensource.zalan.do/acid/postgres-operator:v1.6.0
• Where do you run it - cloud or metal? Kubernetes or OpenShift? GKE
• Are you running Postgres Operator in production? yes
• Type of issue? feature request

Start with the Postgres Operator's Custom Resource Definition and the code that prepares default users' search_path. Check how prepared databases currently omit the public schema and how cluster configuration is exposed through the CRD. Done means users can choose whether public is included and the behavior is covered by the relevant operator checks.