Add design diagrams

Author: lmanohara

README.md

@@ -9,6 +9,85 @@ The suite includes:
 
 This project showcases lightweight, end-to-end request handling, proxying, and server communication in Go, all without third-party frameworks.
 
+### Highlevel Design
+
+```mermaid
+graph TD
+    Client -->|HTTPS Requests| ForwardProxy[Forward Proxy]
+    ForwardProxy -->|Proxied Requests| ReverseProxy[Reverse Proxy]
+    ReverseProxy -->|Routed Requests| HTTPServer1[HTTP Server 1]
+    ReverseProxy -->|Routed Requests| HTTPServer2[HTTP Server 2]
+    HTTPServer1 -->|Responses| ReverseProxy
+    HTTPServer2 -->|Responses| ReverseProxy
+    ReverseProxy -->|Proxied Responses| ForwardProxy
+    ForwardProxy -->|Responses| Client
+```
+### TLS Communication Flow
+
+```mermaid
+sequenceDiagram
+    participant Client
+    participant ForwardProxy as Forward Proxy<br/>Port: 6443<br/>(TLS Server)
+    participant ReverseProxy as Reverse Proxy<br/>Port: 7443<br/>(TLS Server)
+    participant HTTPServer as HTTP Server<br/>Port: 8443<br/>(mTLS Server)
+
+    Note over Client,HTTPServer: Phase 1: Client → Forward Proxy TLS
+
+    Client->>ForwardProxy: TLS Client Hello (TLSv1.3) with CA Certificate
+    ForwardProxy->>Client: Server Hello + Certificate Chain
+    Note right of ForwardProxy: CN=server<br/>Issuer: forward-proxy Root CA<br/>SAN: 127.0.0.1
+    ForwardProxy->>Client: Certificate Verify + Finished
+    Client->>ForwardProxy: Finished
+    Note over Client,ForwardProxy: TLS Connection Established
+
+    Note over Client,HTTPServer: Phase 2: HTTP CONNECT Tunnel
+
+    Client->>ForwardProxy: CONNECT reverse-proxy-server:7443 HTTP/1.1<br/>Host: reverse-proxy-server:7443<br/>Proxy-Connection: Keep-Alive
+    ForwardProxy->>Client: HTTP/1.1 200 Connection Established
+    Note over Client,ForwardProxy: CONNECT Tunnel Established
+
+    Note over Client,HTTPServer: Phase 3: Client → Reverse Proxy TLS (through tunnel)
+
+    Client->>ReverseProxy: TLS Client Hello (TLSv1.3)<br/>via Forward Proxy tunnel
+    ReverseProxy->>Client: Server Hello + Certificate Chain<br/>via Forward Proxy tunnel
+    Note right of ReverseProxy: CN=server<br/>Issuer: reverse-proxy Root CA<br/>SAN: reverse-proxy-server
+    ReverseProxy->>Client: Certificate Verify + Finished<br/>via Forward Proxy tunnel
+    Client->>ReverseProxy: Finished<br/>via Forward Proxy tunnel
+    Note over Client,ReverseProxy: End-to-End TLS Established
+
+    Note over Client,HTTPServer: Phase 4: HTTP Request/Response
+
+    Client->>ReverseProxy: GET /server1 HTTP/1.1<br/>Host: reverse-proxy-server:7443<br/>Accept: */*
+    
+    Note over ReverseProxy,HTTPServer: Phase 5: Reverse Proxy → HTTP Server mTLS
+    
+    ReverseProxy->>HTTPServer: mTLS Handshake (Client Cert Required)
+    HTTPServer->>ReverseProxy: Server Certificate + Client Cert Request
+    ReverseProxy->>HTTPServer: Client Certificate + Finished
+    HTTPServer->>ReverseProxy: Certificate Verify + Finished
+    Note over ReverseProxy,HTTPServer: mTLS Connection Established
+    
+    ReverseProxy->>HTTPServer: GET /server1 HTTP/1.1 (over mTLS)
+    HTTPServer->>ReverseProxy: HTTP/1.1 200 OK<br/>Content-Type: text/html
+    
+    ReverseProxy->>Client: HTTP/1.1 200 OK<br/>Content-Type: text/html<br/>Connection: close<br/><br/>Hello from Server 1
+
+    Note over Client,HTTPServer: Certificate Chain Verification
+
+    rect rgb(240, 248, 255)
+        Note over ForwardProxy: Server Cert: CN=server<br/>CA: forward-proxy Root CA<br/>Validates: --proxy-cacert ca.crt
+    end
+
+    rect rgb(255, 248, 240)
+        Note over ReverseProxy: Server Cert: CN=server<br/>CA: reverse-proxy Root CA<br/>Validates: --cacert ca.crt
+    end
+
+    rect rgb(248, 255, 240)
+        Note over HTTPServer: mTLS Required<br/>Client + Server Certificates<br/>Mutual Authentication
+    end
+```
+
+
 ---
 
 ## Project Structure
@@ -84,6 +163,7 @@ Server 1:
 
 ```bash
 curl -v -x http://127.0.0.1:6790 http://reverse-proxy-server:7090/server1
+curl -v -x https://127.0.0.1:6443 --proxy-cacert ca.crt http://reverse-proxy-server:7090/server1
 ```
 
 Server 2: