docs: diagram on successful write workflow

Motivation: Got curious about what the flow of a client writing to a file would look like.

Modification: Adding two mermaid diagrams that show the flow of a successful write for supported protocols, specifically steps 14 and 15.

Result: Help someone understand some concepts better.

Acked-by: Tigran Mkrtchyan
Target: master
Require-book: no
Require-notes: no

modules/dcache/README.md

@@ -34,6 +34,42 @@ sequenceDiagram
     Door-->>Client: OK
 ```
 
+## Door workflow on successful write, close through door (NFS)
+
+```mermaid
+sequenceDiagram
+    autonumber
+    participant Client
+    participant Door
+    participant poolA
+    participant PoolManager
+    participant PnfsManager
+    participant Billing
+    Client ->> Door: PUT
+    Door->>PnfsManager: PnfsGetFileAttributes (path|pnfsid)
+    PnfsManager -->> Door: storage info, attrs
+    
+    Door ->> PoolManager: PoolMgrSelectWritePoolMsg(pnfsid, storage info)
+    PoolManager-->>Door: poolA
+    Door->>poolA: Start Mover (pnfsid, protocol, storage info)
+    poolA -->>Door: mover id
+    poolA-->>Door: redirect
+    Door -->> Client: redirect
+    loop Application IO
+        Client->>poolA: PUT
+        poolA-->>Client: 'writebytes'
+    end
+    Client->>Door: CLOSE
+    Door->>poolA: Kill Mover(id)
+    poolA->>PnfsManager: PnfsSetFileAttributes
+    PnfsManager-->>poolA: OK
+    poolA ->> Billing: MoverInfoMessage
+    poolA-->>Door: DoorTransferFinishedMessage(status)
+    Door->>Billing: DoorRequestInfoMessage
+    Door-->>Client: OK
+```
+
+
 ## Door workflow on successful read, close through pool (dcap, xroot, http)
 
 ```mermaid
@@ -67,3 +103,37 @@ sequenceDiagram
         Door-->>Client: OK
     end
 ```
+
+## Door workflow on successful write, close through door (dcap, xroot, http)
+```mermaid
+sequenceDiagram
+    autonumber
+    participant Client
+    participant Door
+    participant poolA
+    participant PoolManager
+    participant PnfsManager
+    participant Billing
+    Client ->> Door: PUT
+    Door->>PnfsManager: PnfsCreateEntryMessage (path|pnfsid)
+    PnfsManager -->> Door: storage info, attrs
+    
+    Door ->> PoolManager: PoolMgrSelectWritePoolMsg(pnfsid, storage info)
+    PoolManager-->>Door: poolA
+    Door->>poolA: Start Mover (pnfsid, protocol, storage info)
+    poolA -->>Door: mover id
+    poolA-->>Door: redirect
+    Door -->> Client: redirect
+    loop Application IO
+        Client->>poolA: PUT
+        poolA-->>Client: 'writebytes'
+    end
+    Client->>Door: CLOSE
+    Door->>poolA: Kill Mover(id)
+    poolA->>PnfsManager: PnfsSetFileAttributes
+    PnfsManager-->>poolA: OK
+    poolA ->> Billing: MoverInfoMessage
+    poolA-->>Door: DoorTransferFinishedMessage(status)
+    Door->>Billing: DoorRequestInfoMessage
+    Door-->>Client: OK
+```