Add SAML support

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/server/auth/saml_metadata_handler.go

@@ -0,0 +1,38 @@
+// 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 auth
+
+import (
+	"fmt"
+	"net/http"
+
+	authsvc "github.com/getprobo/probo/pkg/auth"
+)
+
+// SAMLMetadataHandler returns an HTTP handler that serves the SAML Service Provider metadata XML
+// Uses global SP certificate configured at service startup
+func SAMLMetadataHandler(samlSvc *authsvc.SAMLService) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		metadataXML, err := samlSvc.GenerateMetadata()
+		if err != nil {
+			http.Error(w, fmt.Sprintf("failed to generate metadata: %v", err), http.StatusInternalServerError)
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/samlmetadata+xml")
+		w.WriteHeader(http.StatusOK)
+		w.Write(metadataXML)
+	}
+}