Replace hard-coded Basic auth header with -u flag in curl examples in documentation

[coderabbitai]

Summary

In the documentation (e.g., event-gateway/README.md and related files), curl examples embed credentials as a Base64-encoded Authorization: Basic header literal (e.g., --header 'Authorization: Basic YWRtaW46YWRtaW4='). This should be replaced with curl's -u option (e.g., -u admin:admin or -u <user>:<pass>) for clarity and to avoid publishing credential-like encoded strings directly in documentation.

References

• PR: Add implementation for WebBrokerAPIs #1954
• Review comment: Add implementation for WebBrokerAPIs #1954 (comment)
• Related comments in PR [DO NOT MERGE] Add Implementation for Exposing Brokers as Subscribable APIs over Web-friendly Protocols #1944

Requested by

@senthuran16