Add CREATE SCHEMA ... LIKE support

Hi hackers

I was reading the TODO wiki page and found the "Add CREATE SCHEMA ...
LIKE that copies a schema" item and I thought that it could be a good
idea to have this at core.

It's common for certain applications to have a different schema for each
customer and having a built-in way to copy an entire schema could be
useful for this use case.

I'd like to propose the introduction of the LIKE syntax on CREATE SCHEMA
command with the following syntax:
  CREATE SCHEMA <name> LIKE <source_schema> [like_options...]

Where like_options is:
  { INCLUDING | EXCLUDING } { TABLE | INDEX | ... | ALL }

The idea of LIKE syntax is to create a new schema with all objects that
exist on source schema like tables, indexes, sequences, functions,
views, etc.

I'm attaching a PoC patch that implements the LIKE syntax for tables and
indexes. I would like to start a discussion to see if this feature make
sense and if it could be useful to have at core. I have intention to add
support for more objects(sequence, functions, ...) in future patches if
It makes sense.

Thoughts?

--
Matheus Alcantara
EDB: https://www.enterprisedb.com