update the mirsg.infrastructure.postgresql role README to reflect that it is now part of this collection rather than a standalone role
add a workflow and testing the role, as well as the converge and prepare steps
the workflow for this role runs mirsg.infrastructure.provision before mirsg.infrastructure.postgresql, otherwise we'd need to duplicate a lot of what the provision role does (e.g set correct locale, disable any running postgresql service, install gpg key)
mirsg.infrastructure.postgresqlrole README to reflect that it is now part of this collection rather than a standalone rolemirsg.infrastructure.provisionbeforemirsg.infrastructure.postgresql, otherwise we'd need to duplicate a lot of what the provision role does (e.g set correct locale, disable any running postgresql service, install gpg key)