Disambiguate from keyword in CTO syntax

[mttrbrts]

Discussion 🗣

In the pre-release version of Concerto v3 we use from to mean different things:

// Meaning "from" a namespace"
import { Foo, Bar } from [email protected].

// Meaning "from" a URI 
import [email protected] from github://path/to/file.cto

This has the effect of restricting the selective imports available for external dependencies, i.e. the following is not possible today.

import { Foo, Bar } from [email protected] from github://path/to/file.cto

I propose that we change the syntax in Concerto v3 to improve the semantics of the keywords and standardise on import syntax.

Some ideas:

import [email protected]
import [email protected].{ Foo, Bar }
import [email protected].*
import [email protected] from github://path/to/file.cto 
import [email protected].{ Foo, Bar } from github://path/to/file.cto 
import [email protected].* from github://path/to/file.cto 

import Foo from [email protected]
import { Foo, Bar } from [email protected]
import * from [email protected] 
import Foo from [email protected] using github://path/to/file.cto 
import { Foo, Bar } from [email protected] using github://path/to/file.cto 
import * from [email protected] using github://path/to/file.cto 

This issue could be tackled alongside #480.