IAM-683 feat: add `PATCH /identities/{identityID}/{entitlements,groups,roles}`

[BarcoMasile]

Description

Implemented the three missing endpoints (and relative tests) from #200 .

Changes

• Implemented endpoints:
  • PATCH /identities/{id}/entitlements
  • PATCH /identities/{id}/groups
  • PATCH /identities/{id}/roles
• relative unit tests
• added unit tests for ValidationErrors
• updated generated code from latest spec
• adjusted existing code to latest generated code
• refactored http status code to leverage http package