Feature/ccm 12274 update diagrams (#33)

* CCM-12274: Updated sequence diagram to incorporate review feedback
* CCM-12274: Added sequence diagram for mesh poll/retrieve
* CCM-12274: Changed MeshPoll trigger to be a scheduled event & added SQS

---------

Co-authored-by: Ross Buggins (NHS) <[email protected]>

Author: tdroza-nhs

docs/diagrams/digital-letters-sequence.md

@@ -36,7 +36,10 @@ sequenceDiagram
   participant nhsapp as NHSApp
 
 
-  trust -> notify-letters: MESH (CommunicationRequest)
+  trust ->> notify-letters: MESH (CommunicationRequest)
+  activate notify-letters
+      notify-letters ->> trust: MESH Ack
+  deactivate notify-letters
   notify-letters ->> notify-letters: Store CommunicationRequest (S3)
   notify-letters ->> notify-letters: Create SendLetter TTL
   notify-letters ->> pdm: POST /CommunicationRequest
@@ -68,6 +71,11 @@ sequenceDiagram
     notify-letters ->> notify-letters: Delete SendLetterTTL
   else Read receipt not received within print expiry time
     notify-letters ->> notify-letters: SendLetter TTL expires
-    notify-letters ->> notify-supplier: SendLetter Event
+    notify-letters -) notify-supplier: SendLetter Event
+    notify-supplier -) notify-letters: Letter Status Events
   end
+  opt Daily status reports
+    notify-letters -) trust: CSV via MESH
+  end
+
 ```

docs/diagrams/mesh-sequence.md

@@ -0,0 +1,48 @@
+---
+layout: page
+title: MESH
+nav_order: 3
+parent: Diagrams
+has_children: false
+child_nav_order: reversed
+is_not_draft: false
+last_modified_date: 2025-10-10
+owner: Tom D'Roza
+author: Tom D'Roza
+---
+
+```mermaid
+
+sequenceDiagram
+  actor trust as Trust
+  participant meshMailbox as MESH<br/>Mailbox
+  participant meshPoll as Lambda<br/>MESHPoll
+  participant eventBus as EventBus
+  participant sqs as SQS<br/>MeshRetrieveQueue
+  participant meshRetrieve  as Lambda<br/>MESHRetrieve
+  participant s3 as S3<br/>DigitalLettersBucket
+
+  trust ->> meshMailbox: MESH (CommunicationRequest)
+  activate meshMailbox
+    meshMailbox ->> trust: MESH Ack
+  deactivate meshMailbox
+
+  Loop Interval TBC
+    eventBus -) meshPoll: Scheduled event
+    activate meshPoll
+  end
+  meshPoll ->> meshMailbox: Check for new files
+  meshPoll -) eventBus: NewFileReceived Event(meshFileId)
+  deactivate meshPoll
+
+  eventBus -) sqs: NewFileReceived(meshFileId)
+  sqs -) meshRetrieve: NewFileReceived(meshFileId)
+  activate meshRetrieve
+    meshRetrieve ->> meshMailbox: Retrieve file(meshFileId)
+    activate meshMailbox
+      meshMailbox -->> meshRetrieve: File
+    deactivate meshMailbox
+    meshRetrieve ->> s3: Upload file
+    meshRetrieve -) eventBus: FileUploaded(S3FileId) Event
+  deactivate meshRetrieve
+```