Incorrect versioning and changelog references

[clundie-CL]

Problem description
Related to review comments included with PR #73

The CHANGELOG.md and Readiness Checklist documents currently reference CAMARA Commonalities version 0.5 (r2.3), while the OpenAPI specification (network-access-management.yaml) references version 0.6 (currently r3.2). This inconsistency in documentation may cause confusion regarding which Commonalities version the API is aligned with.

Expected behavior
Both CHANGELOG.md and Readiness Checklist should be updated to reference CAMARA Commonalities version 0.6, ensuring consistency with the API specification and clarity for reviewers and implementers.

Alternative solution
Alternatively, if the API is not yet fully compliant with Commonalities 0.6, revert the OpenAPI specification to reference version 0.5 until full alignment is achieved.

Additional context
This issue was identified during the alpha release review. Consistent documentation of the Commonalities version is required for CAMARA compliance and to avoid confusion during future