Add Chef package registry (#22554)

This PR implements a [Chef registry](https://chef.io/) to manage
cookbooks. This package type was a bit complicated because Chef uses RSA
signed requests as authentication with the registry.


![grafik](https://user-images.githubusercontent.com/1666336/213747995-46819fd8-c3d6-45a2-afd4-a4c3c8505a4a.png)


![grafik](https://user-images.githubusercontent.com/1666336/213748145-d01c9e81-d4dd-41e3-a3cc-8241862c3166.png)

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

routers/web/user/setting/packages.go

@@ -5,10 +5,14 @@ package setting
 
 import (
 	"net/http"
+	"strings"
 
+	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/context"
+	chef_module "code.gitea.io/gitea/modules/packages/chef"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 	shared "code.gitea.io/gitea/routers/web/shared/packages"
 )
 
@@ -95,3 +99,21 @@ func RebuildCargoIndex(ctx *context.Context) {
 
 	ctx.Redirect(setting.AppSubURL + "/user/settings/packages")
 }
+
+func RegenerateChefKeyPair(ctx *context.Context) {
+	priv, pub, err := util.GenerateKeyPair(chef_module.KeyBits)
+	if err != nil {
+		ctx.ServerError("GenerateKeyPair", err)
+		return
+	}
+
+	if err := user_model.SetUserSetting(ctx.Doer.ID, chef_module.SettingPublicPem, pub); err != nil {
+		ctx.ServerError("SetUserSetting", err)
+		return
+	}
+
+	ctx.ServeContent(strings.NewReader(priv), &context.ServeHeaderOptions{
+		ContentType: "application/x-pem-file",
+		Filename:    ctx.Doer.Name + ".priv",
+	})
+}