Add Cargo package registry (#21888)

This PR implements a [Cargo registry](https://doc.rust-lang.org/cargo/)
to manage Rust packages. This package type was a little bit more
complicated because Cargo needs an additional Git repository to store
its package index.

Screenshots:

![grafik](https://user-images.githubusercontent.com/1666336/203102004-08d812ac-c066-4969-9bda-2fed818554eb.png)

![grafik](https://user-images.githubusercontent.com/1666336/203102141-d9970f14-dca6-4174-b17a-50ba1bd79087.png)

![grafik](https://user-images.githubusercontent.com/1666336/203102244-dc05743b-78b6-4d97-998e-ef76341a978f.png)

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/packages/package.go

@@ -30,6 +30,7 @@ type Type string
 
 // List of supported packages
 const (
+	TypeCargo     Type = "cargo"
 	TypeComposer  Type = "composer"
 	TypeConan     Type = "conan"
 	TypeConda     Type = "conda"
@@ -46,6 +47,7 @@ const (
 )
 
 var TypeList = []Type{
+	TypeCargo,
 	TypeComposer,
 	TypeConan,
 	TypeConda,
@@ -64,6 +66,8 @@ var TypeList = []Type{
 // Name gets the name of the package type
 func (pt Type) Name() string {
 	switch pt {
+	case TypeCargo:
+		return "Cargo"
 	case TypeComposer:
 		return "Composer"
 	case TypeConan:
@@ -97,6 +101,8 @@ func (pt Type) Name() string {
 // SVGName gets the name of the package type svg image
 func (pt Type) SVGName() string {
 	switch pt {
+	case TypeCargo:
+		return "gitea-cargo"
 	case TypeComposer:
 		return "gitea-composer"
 	case TypeConan: