Add gems remote type for RubyGems

- add gems package type proxying the compact index and .gem/quick gemspec downloads
- route HEAD on /api/v1/remote/* so gem detects the compact index

internal/api/v1/proxy.go

@@ -40,6 +40,7 @@ func NewProxyHandler(engine *proxy.Engine, virtualEngine *virtual.Engine, db *da
 func (h *ProxyHandler) Routes() chi.Router {
 	r := chi.NewRouter()
 	r.Get("/remote/{remoteName}/*", h.handleProxy)
+	r.Head("/remote/{remoteName}/*", h.handleProxyHead)
 	r.Get("/local/{localName}/*", h.handleLocal)
 	r.Get("/virtual/{virtualName}/*", h.handleVirtual)
 	return r

internal/api/v1/routes_test.go

@@ -0,0 +1,17 @@
+package v1
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+)
+
+func TestRoutesRemoteHead(t *testing.T) {
+	r := (&ProxyHandler{}).Routes()
+	for _, m := range []string{http.MethodGet, http.MethodHead} {
+		if !r.Match(chi.NewRouteContext(), m, "/remote/rubygems/versions") {
+			t.Errorf("%s /remote/rubygems/versions not routed", m)
+		}
+	}
+}