Vizualize write path for a vault in meta secret (#62)

Signed-off-by: metacat <[email protected]>

docs/vault_write_path.md

@@ -0,0 +1,50 @@
+### Meta Secret
+
+#### Vault "write path"
+
+```mermaid
+
+flowchart TD
+    subgraph "meta_secret (vault: write)"
+        direction TB
+
+        subgraph clients
+            client_a
+            client_b
+            client_c
+        end
+
+        subgraph server
+            subgraph server_db
+                device_log_a[(device_log_a)]
+                device_log_b[(device_log_b)]
+                device_log_c[(device_log_c)]
+
+                vault_log[(vault_log)]
+                vault[(vault)]
+                
+                vault_status_a[(vault_status_a)]
+                vault_status_b[(vault_status_b)]
+                vault_status_c[(vault_status_c)]
+            end
+
+            client_a--device_log_a-->server_app_writes
+
+            client_b--device_log_b-->server_app_writes
+            client_c--device_log_c-->server_app_writes
+
+            server_app_writes--save-->device_log_a
+            server_app_writes--save-->device_log_b
+            server_app_writes--save-->device_log_c
+
+            device_log_a--enqueue-->vault_log
+            device_log_b--enqueue-->vault_log
+            device_log_c--enqueue-->vault_log
+            vault_log--create||update-->vault
+            
+            vault--update_status-->vault_status_a
+            vault--update_status-->vault_status_b
+            vault--update_status-->vault_status_c
+        end
+    end
+