cronjobs added

Writerside/c.tree

@@ -9,6 +9,7 @@
     <toc-element topic="Home.topic">
     </toc-element>
     <toc-element topic="Developer.md">
+        <toc-element topic="Cronjobs.md"/>
         <toc-element topic="Running-Tests.md"/>
         <toc-element topic="Getting-Started.md"/>
         <toc-element topic="Debugging.md"/>

Writerside/topics/Cronjobs.md

@@ -0,0 +1,22 @@
+# Cronjobs
+
+## Running regular cronjobs
+Crons are run by executing the CronCommand from the command line.
+By default this will run all available cronjobs not run in the last 23 hours.
+
+```bash
+    bin/console commsy:cron:main
+```
+
+## How cronjobs are processed
+Running a cron will dispatch an async message, that will be picked up
+by a runner and finally performed.
+If a job is successfull another message is dispatched to update the last
+run in the cron table.
+
+```mermaid
+graph TB
+    A[Cron execution] -- dispatch --> B([CronTaskRun Message])
+    B -- handled by --> C(Message Worker)
+    C -- dispatch --> D([CronTaskFinished Message])
+```