Align subscription-status with Sync26 RC requirements

[chinaunicomyangfan]

What type of PR is this?

correction

What this PR does / why we need it:

This PR aligns the SubscriptionStatus repository with the Sync26 r2.1 RC release requirements.

It updates the API definition to match the current Commonalities / ICM expectations, fixes the retrive -> retrieve naming inconsistency in the endpoint path, OAuth scope, tag, and operationId, and aligns the 3-legged token behavior with UNNECESSARY_IDENTIFIER.

It also updates the BDD test definition and refreshes the API readiness checklist so the repository is ready for the next release-automation steps.

Special notes for reviewers:

• version: wip is intentionally kept unchanged on main
• README.md and CHANGELOG.MD were intentionally not updated manually
• CHANGELOG-r2.1.md should be generated and completed later in the release-review flow
• Main functional changes in this PR:
  • align mandatory info.description blocks with current templates
  • update x-camara-commonalities to 0.8.0
  • reuse common CAMARA definitions for openId, x-correlator, PhoneNumber, and ErrorInfo
  • add the UNNECESSARY_IDENTIFIER test scenario
  • refresh the readiness checklist from v0.1.0 / r1.2 to v0.2.0 / r2.1

Changelog input

[ChuanyuChen]

Looks good to me