changing format for recipient id ,event id custom attributes as per cloud events spec

[abhupadh]

Description

Changing format for custom attributes added by Adobe I/O Events in its delivered cloud events payload so that they comply to the spec. cf https://github.com/cloudevents/spec/blob/main/cloudevents/spec.md#naming-conventions

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[abhupadh]

closing this as java11 branch is not needed to be maintained