Clarify migrations diagram

Author: samdark

src/guide/databases/db-migrations.md

@@ -23,17 +23,23 @@ And the following steps show how to deploy a new release with database migration
 3. Scott applies any accumulated database migrations to the production database.
 
 ```mermaid
-flowchart LR
-    subgraph Development
-        create[Create migration] --> commit[Commit migration]
-        commit --> pull[Pull changes]
-        pull --> applyLocal[Apply migration locally]
-    end
-
-    subgraph Production
-        tag[Create release tag] --> deploy[Update source on server]
-        deploy --> applyProd[Apply pending migrations]
-    end
+sequenceDiagram
+    participant Tim
+    participant VCS as Source control
+    participant Doug
+    participant LocalDB as Local development database
+    participant Scott
+    participant ProdServer as Production server
+    participant ProdDB as Production database
+
+    Tim->>Tim: Creates a new migration
+    Tim->>VCS: Commits the new migration
+    Doug->>VCS: Updates his repository and receives the new migration
+    Doug->>LocalDB: Applies the migration locally
+
+    Scott->>VCS: Creates a release tag with new migrations
+    Scott->>ProdServer: Updates source code to the release tag
+    Scott->>ProdDB: Applies accumulated migrations
 ```
 
 Yii provides a set of migration command line tools that allow you to: