discv5: put diagram source into an external file

Author: fjl

discv5/discv5-theory.md

@@ -369,23 +369,7 @@ each message in the diagram below. We use these abbreviations:
 - `H(X)`: [handshake message packet] containing request `X`
 - `s(M)`: [session message packet] containing message `M`
 
-<?mermaid
-    sequenceDiagram
-        participant Alice
-        participant Relay
-        participant Bob
-
-        Relay-->>Alice: s(NODES[Bob's ENR])
-        Alice->>Bob: m(nonce,FINDNODE)
-        Note left of Alice:Hole punched in Alice's NAT for Bob
-        Note left of Alice:FINDNODE timed out
-        Alice->>Relay: s(RELAYINIT[nonce])
-        Relay->>Bob: s(RELAYMSG[nonce])
-        Bob-->>Alice: whoareyou(nonce)
-        Note right of Bob: Hole punched in Bob's NAT for Alice
-        Alice-->>Bob: H(FINDNODE)
-?>
-
+<!-- diagram source: ./img/nat-hole-punching-flow.mermaid -->
 ![Diagram](./img/nat-hole-punching-flow.svg)
 
 Preconditions: Bob is behind NAT. Bob is contained in Relay's node table, they have an

discv5/img/nat-hole-punching-flow.mermaid

@@ -0,0 +1,14 @@
+sequenceDiagram
+    participant Alice
+    participant Relay
+    participant Bob
+
+    Relay-->>Alice: s(NODES[Bob's ENR])
+    Alice->>Bob: m(nonce,FINDNODE)
+    Note left of Alice:Hole punched in Alice's NAT for Bob
+    Note left of Alice:FINDNODE timed out
+    Alice->>Relay: s(RELAYINIT[nonce])
+    Relay->>Bob: s(RELAYMSG[nonce])
+    Bob-->>Alice: whoareyou(nonce)
+    Note right of Bob: Hole punched in Bob's NAT for Alice
+    Alice-->>Bob: H(FINDNODE)