xmpp-connection-finite-state-machine.md

+Here is a summary of the XMPP connection finite state machine used by ibex.
+
+[Original graph](https://adiaholic.github.io/gsoc2020/2020/07/12/Chapter-8-Reworking-FSM.html) was made by Aditya Borikar.
+
+```mermaid
+graph TD
+    Disconnected{{XMPP Client Disconnected}} -->|start connection| DirectTLS(Connect with direct TLS)
+    DirectTLS -->|TLS connection failure| TCPConnect(Connect with StartTLS)
+    TCPConnect -->|TCP connection success| TCPConnected{{TCP connected}}
+    TCPConnected -->|send <stream:stream>| NotSecureXmppStreamInitiated{{XMPP Stream initiated and not encrypted}}
+    NotSecureXmppStreamInitiated -->|find starttls stream feature and send <starttls>| beginStartTls{Start StartTLS}
+    beginStartTls -->|server accepts starttls| XmppStreamInitiated
+    beginStartTls -->|server refuses starttls| Disconnected
+    DirectTLS -->|TLS connection success| XmppStreamInitiated{{XMPP Stream initiated with secure connection}}
+
+```
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