raposza/tools: platform/raposza-test-idp/README.md

<!-- Copyright (c) 2026 bentzn --> <!-- SPDX-License-Identifier: Apache-2.0 --> # raposza-test-idp Local test identity provider. Must be structurally incapable of reaching a production configuration. ## What it serves ``` GET /.well-known/openid-configuration issuer, token_endpoint, jwks_uri GET /jw