Merged PR 880350: feat: Add auditlog deprecation notice

Security-concept-update-needed: false.

JIRA Work Item: [STACKITRMA-647](https://jira.schwarz/browse/STACKITRMA-647)

README.md

@@ -1,3 +1,35 @@
+> ## DEPRECATION NOTICE  
+> 
+> ### Discontinuation of the current audit log system
+>
+> The audit log system provided to date will be discontinued in its current form. 
+> This decision was made to pave the way for a new, more powerful audit log system that 
+> will be provided in the future. The new system offers extended functionalities and 
+> improved integration options, particularly with regard to the use and analysis of 
+> audit data by our customers.  
+>   
+> ### What does it mean?
+> The existing audit log system will be supported until the new system is generally 
+> available to customers on Mai 1, 2026.  
+> **Services that are already sending audit log events to the existing audit log 
+> system must continue to do so until the new system is GA** and further information 
+> about the shutdown process is provided.  
+> **Large volumes of new audit event types must not be sent to the existing audit log
+> system.**  
+>
+> STACKIT services should start migrating to the new system now by sending data to 
+> the new system (**in parallel**).  
+> **The new audit log system may drop and does not guarantee to store events until 
+> it will be GA**.  
+> Further information on the changeover and how to use the new system can be found in the
+> [developer docs](https://developers.stackit.schwarz/domains/central-services/telemetry-router/integration/).  
+> 
+> We are confident that the new audit log system will make an important contribution to 
+> improving the transparency, traceability, and integration for our customers. 
+> If you have any questions or need assistance, the 
+> [STACKIT Telemetry Hub](https://chat.google.com/room/AAQAf9NsX6M?cls=7) team will be 
+> happy to help.  
+
 ## audit-go
 
 The audit-go library is the core library for validation and sending of audit events.