Extract authn & authz utils

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/server/api/authn/identity_presence_middleware.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package authn
+
+import (
+	"net/http"
+
+	"github.com/99designs/gqlgen/graphql"
+	"github.com/vektah/gqlparser/v2/gqlerror"
+	"go.gearno.de/kit/httpserver"
+	"go.probo.inc/probo/pkg/server/gqlutils"
+)
+
+func NewIdentityPresenceMiddleware() func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(
+			func(w http.ResponseWriter, r *http.Request) {
+				identity := IdentityFromContext(r.Context())
+
+				if identity == nil {
+					httpserver.RenderJSON(
+						w,
+						http.StatusUnauthorized,
+						&graphql.Response{
+							Errors: gqlerror.List{
+								gqlutils.Unauthenticatedf(
+									r.Context(),
+									"authentication is required to access this resouce",
+								),
+							},
+						},
+					)
+					return
+				}
+
+				next.ServeHTTP(w, r)
+			},
+		)
+	}
+}