docs(example): simplified deletion

[mqf20]

Description

This PR updates the example.

It simplifies the deletion of refresh tokens and associated access tokens by storing a pointer from the refresh token to the access token.

Definition of Ready

• I am happy with the code
• Short description of the feature/issue is added in the pr description
• PR is linked to the corresponding user story
• Acceptance criteria are met
• All open todos and follow ups are defined in a new ticket and justified
• Deviations from the acceptance criteria and design are agreed with the PO and documented.
• No debug or dead code
• My code has no repetitions
• Critical parts are tested automatically
• Where possible E2E tests are implemented
• Documentation/examples are up-to-date
• All non-functional requirements are met
• Functionality of the acceptance criteria is checked manually on the dev system.

[muhlemmer]

Waiting for #698 (comment) to be applied.