Add selective Mermaid diagrams

Author: samdark

src/guide/concept/di-container.md

@@ -118,6 +118,22 @@ That's what dependency containers are for.
 A dependency injection (DI) container is an object that knows how to instantiate and configure objects and
 all objects they depend on.
 
+At runtime, application code declares dependencies. The container uses configuration and type declarations to build
+these objects and the objects they depend on:
+
+```mermaid
+flowchart TD
+    action[Action handler] -->|declares dependency| service[ReportService]
+    container[DI container] -->|injects| service
+    service -->|needs| cache[CacheInterface]
+    service -->|needs| db[ConnectionInterface]
+    container -->|creates and configures| service
+    container -->|resolves| cache
+    container -->|resolves| db
+    definitions[Container definitions] -.-> container
+    types[Constructor types] -.-> container
+```
+
 Yii provides the DI container feature through the [yiisoft/di](https://github.com/yiisoft/di) package and
 [yiisoft/injector](https://github.com/yiisoft/injector) package.
 

src/guide/databases/db-migrations.md

@@ -22,6 +22,20 @@ And the following steps show how to deploy a new release with database migration
 2. Scott updates the source code on the production server to the release tag.
 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
+```
+
 Yii provides a set of migration command line tools that allow you to:
 
 * create new migrations;

src/internals/016-security-workflow.md

@@ -5,6 +5,24 @@ Security issues are typically sent via [a security form](https://www.yiiframewor
 If an issue is reported directly to a public page such as a repository issue or a forum topic, get the message
 and delete the issue. Say thanks to the reporter and point to the security form for next time.  
 
+```mermaid
+flowchart TD
+    form[Security form report] --> verify[Verify issue]
+    public[Public report] --> remove[Save details and delete public issue]
+    remove --> redirect[Point reporter to the security form]
+    redirect --> verify
+    verify -->|needs details| requestInfo[Request more information]
+    requestInfo --> verify
+    verify -->|valid| advisory[Create draft security advisory]
+    advisory --> severity[Set CVSS severity]
+    severity --> credit[Ask about reporter credit]
+    credit --> cve[Request CVE number]
+    cve --> patch[Prepare patch pull request]
+    patch --> wait[Wait for CVE allocation]
+    wait --> release[Release]
+    release --> publish[Publish advisory and submit FriendsOfPHP entry]
+```
+
 ## Verify
 
 Verify that the issue is valid. Request more information if needed.