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/request_context.go

@@ -0,0 +1,48 @@
+// 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
+
+import (
+	"context"
+
+	"go.probo.inc/probo/pkg/coredata"
+)
+
+type contextKey struct{ name string }
+
+var (
+	accessTokenContextKey = &contextKey{name: "oauth2_access_token"}
+	clientContextKey      = &contextKey{name: "oauth2_client"}
+)
+
+func ContextWithAccessToken(ctx context.Context, accessToken *coredata.OAuth2AccessToken) context.Context {
+	return context.WithValue(ctx, accessTokenContextKey, accessToken)
+}
+
+func AccessTokenFromContext(ctx context.Context) (*coredata.OAuth2AccessToken, bool) {
+	accessToken, ok := ctx.Value(accessTokenContextKey).(*coredata.OAuth2AccessToken)
+
+	return accessToken, ok
+}
+
+func ContextWithClient(ctx context.Context, client *coredata.OAuth2Client) context.Context {
+	return context.WithValue(ctx, clientContextKey, client)
+}
+
+func ClientFromContext(ctx context.Context) (*coredata.OAuth2Client, bool) {
+	client, ok := ctx.Value(clientContextKey).(*coredata.OAuth2Client)
+
+	return client, ok
+}