[Feature Request] Schema Aliases and Versioned Schemas

- versioned schemas : where every version act as a separate schema and the `latest` one or the one the program request is the one in use and each new schema could inherit a table, index, view, ... without additional data
- aliases : where every new schema is defined and migrated separately then an alias is set for the one in use

**Benefits:**
- migration process for under dev projects will be more easier

- App env stability, where no data need to be changed in the app other than the logic of newly modified schema, not the connection nor the schema or db name

- no need for external tools or servers to migrate or rollback

- minimal downtime between migrations and rollback

**why I post here**
it's addition to core pgsql
>> if it's not the right place : I could contact the mailing list you know it's supposed to take feature requests

Thank you for considering this feature request.

I look forward to feedback or further discussion on this idea.

Best regards,
Abdelaziz sharaf