semi implemented and features implemented save checkpoint

docs/features/unchecked/gateway/gateway-http-middleware-pipeline.md

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+# Gateway HTTP Middleware Pipeline
+
+## Module
+Gateway
+
+## Status
+IMPLEMENTED
+
+## Description
+Full HTTP middleware pipeline for the Gateway WebService including endpoint resolution, authorization with claims propagation, routing decision, transport dispatch, correlation ID tracking, tenant isolation, health checks, and global error handling.
+
+## Implementation Details
+- **Authorization**: `src/Gateway/StellaOps.Gateway.WebService/Authorization/AuthorizationMiddleware.cs` -- endpoint authorization
+- **Claims propagation**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/ClaimsPropagationMiddleware.cs` -- propagates authenticated claims to downstream services
+- **Correlation ID**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/CorrelationIdMiddleware.cs` -- request correlation tracking
+- **Routing**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/RequestRoutingMiddleware.cs` -- route resolution and dispatch
+- **Routes**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/GatewayRoutes.cs` -- route definitions
+- **Health checks**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/HealthCheckMiddleware.cs`
+- **Identity header policy**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/IdentityHeaderPolicyMiddleware.cs` -- identity header enforcement
+- **Sender constraints**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/SenderConstraintMiddleware.cs`
+- **Tenant isolation**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/TenantMiddleware.cs`
+- **Context keys**: `src/Gateway/StellaOps.Gateway.WebService/Middleware/GatewayContextKeys.cs`
+- **Security**: `src/Gateway/StellaOps.Gateway.WebService/Security/AllowAllAuthenticationHandler.cs`
+- **Source**: batch_51/file_21.md
+
+## E2E Test Plan
+- [ ] Verify middleware pipeline executes in correct order
+- [ ] Test authorization middleware blocks unauthorized requests
+- [ ] Verify correlation IDs propagate through gateway to downstream services
+- [ ] Test tenant isolation prevents cross-tenant access
+- [ ] Verify edge cases and error handling