Add OAuth2 API scope registration and enforcement

Register v1 API scopes in coredata, advertise them in OIDC discovery
and protected-resource metadata, show them on the consent screen, and
enforce scope-to-action mapping in the IAM Authorizer before policy
evaluation.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/iam/oauth2/scope_test.go

@@ -0,0 +1,143 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.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 oauth2_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.probo.inc/probo/pkg/coredata"
+	"go.probo.inc/probo/pkg/iam/oauth2"
+)
+
+func TestIsValid(t *testing.T) {
+	t.Parallel()
+
+	t.Run(
+		"offline_access is valid",
+		func(t *testing.T) {
+			t.Parallel()
+
+			assert.True(t, oauth2.IsValid(oauth2.ScopeOfflineAccess))
+		},
+	)
+
+	t.Run(
+		"unknown scope is invalid",
+		func(t *testing.T) {
+			t.Parallel()
+
+			assert.False(t, oauth2.IsValid(coredata.OAuth2Scope("admin")))
+		},
+	)
+}
+
+func TestUnmarshalScope(t *testing.T) {
+	t.Parallel()
+
+	t.Run(
+		"offline_access unmarshals",
+		func(t *testing.T) {
+			t.Parallel()
+
+			scope, err := oauth2.UnmarshalScope([]byte("offline_access"))
+			assert.NoError(t, err)
+			assert.Equal(t, oauth2.ScopeOfflineAccess, scope)
+		},
+	)
+
+	t.Run(
+		"invalid scope returns error",
+		func(t *testing.T) {
+			t.Parallel()
+
+			_, err := oauth2.UnmarshalScope([]byte("admin"))
+			assert.Error(t, err)
+		},
+	)
+}
+
+func TestOAuth2ScopesContains(t *testing.T) {
+	t.Parallel()
+
+	t.Run(
+		"contains offline_access",
+		func(t *testing.T) {
+			t.Parallel()
+
+			scopes := coredata.OAuth2Scopes{
+				oauth2.ScopeOpenID,
+				oauth2.ScopeOfflineAccess,
+			}
+			assert.True(t, scopes.Contains(oauth2.ScopeOfflineAccess))
+		},
+	)
+
+	t.Run(
+		"does not contain offline_access",
+		func(t *testing.T) {
+			t.Parallel()
+
+			scopes := coredata.OAuth2Scopes{
+				oauth2.ScopeOpenID,
+				oauth2.ScopeProfile,
+			}
+			assert.False(t, scopes.Contains(oauth2.ScopeOfflineAccess))
+		},
+	)
+}
+
+func TestOAuth2ScopesOrDefault(t *testing.T) {
+	t.Parallel()
+
+	defaultScopes := coredata.OAuth2Scopes{
+		oauth2.ScopeOpenID,
+		oauth2.ScopeProfile,
+	}
+
+	t.Run(
+		"returns default when scopes is nil",
+		func(t *testing.T) {
+			t.Parallel()
+
+			var scopes coredata.OAuth2Scopes
+
+			result := scopes.OrDefault(defaultScopes)
+			assert.Equal(t, defaultScopes, result)
+		},
+	)
+
+	t.Run(
+		"returns default when scopes is empty",
+		func(t *testing.T) {
+			t.Parallel()
+
+			scopes := coredata.OAuth2Scopes{}
+			result := scopes.OrDefault(defaultScopes)
+			assert.Equal(t, defaultScopes, result)
+		},
+	)
+
+	t.Run(
+		"returns scopes when non-empty",
+		func(t *testing.T) {
+			t.Parallel()
+
+			scopes := coredata.OAuth2Scopes{oauth2.ScopeEmail}
+			result := scopes.OrDefault(defaultScopes)
+			assert.Equal(t, scopes, result)
+		},
+	)
+}