Put locale in compliance portal URLs

Path-segment locales make each language crawlable with self
canonical and hreflang, while identity.locale persists an
explicit choice without client storage or cookie banners.

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

pkg/server/api/complianceportal/v1/seo_test.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package complianceportal_v1_test
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	complianceportal_v1 "go.probo.inc/probo/pkg/server/api/complianceportal/v1"
+)
+
+func TestSEOFromRequest(t *testing.T) {
+	t.Parallel()
+
+	req, err := http.NewRequest(http.MethodGet, "https://app.example.com/trust/acme/fr/documents", nil)
+	require.NoError(t, err)
+
+	lang, canonical, hreflang := complianceportal_v1.SEOFromRequest(req, "https://app.example.com/trust/acme")
+	assert.Equal(t, "fr", lang)
+	assert.Equal(t, "https://app.example.com/trust/acme/fr/documents", canonical)
+	require.NotEmpty(t, hreflang)
+
+	var xDefault string
+	var enHref string
+	for _, link := range hreflang {
+		if link.Lang == "x-default" {
+			xDefault = link.Href
+		}
+		if link.Lang == "en" {
+			enHref = link.Href
+		}
+	}
+	assert.Equal(t, "https://app.example.com/trust/acme/en/documents", enHref)
+	assert.Equal(t, enHref, xDefault)
+}