Support declaring a default (required?) registry url

[maciektr]

Problem

Dependencies in the Scarb toml manifest can be defined either as version requirement (dep = "1.2.3") or a detailed dependency (dep = { version = "1.2.3", registry = "https://some.registry" }).
This alternatives has been defined in

scarb/scarb/src/core/manifest/toml_manifest.rs

Lines 258 to 279 in 152926a

	pub enum TomlDependency {
	/// [`VersionReq`] specified as a string, e.g. `package = "<version>"`.
	Simple(VersionReq),
	/// Detailed specification as a table, e.g. `package = { version = "<version>" }`.
	Detailed(Box<DetailedTomlDependency>),
	}
	#[derive(Clone, Debug, Default, Deserialize, Serialize)]
	#[serde(rename_all = "kebab-case")]
	pub struct DetailedTomlDependency {
	pub version: Option<VersionReq>,
	/// Relative to the file it appears in.
	pub path: Option<RelativeUtf8PathBuf>,
	pub git: Option<Url>,
	pub branch: Option<String>,
	pub tag: Option<String>,
	pub rev: Option<String>,
	pub registry: Option<Url>,
	}

A detailed dependency of package from registry can define an optional url of the registry that should be used.

In case a dependency is specified as a version requirement (without registry url), a default registry is assumed. The default registry is https://scarbs.xyz/.

Consider adding an option to override default registry.

This could potentially serve to purposes:

• Use different than official registry for testing purposes
• Use a registry that you own and trust to access a limited / audited set of packages only (should it allow specifying different registry url in deps?)

Solving this task should include researching how changing registry to serve dependencies is solved in other package managers.

Also see: #1434

Proposed Solution

No response

Notes

No response