feat: add session_transfer delegation config support for CTE impersonation

[ankita10119]

🔧 Changes

Added support for session_transfer.delegation configuration on clients, enabling the Custom Token Exchange Impersonation via Session Transfer feature (Phase 2).

New optional properties under session_transfer.delegation:

• allow_delegated_access (boolean) — allows clients to accept Session Transfer Tokens that contain an Actor, enabling impersonated SSO sessions
• enforce_device_binding (string: "ip" | "asn") — enforces device binding for impersonation sessions; defaults to "ip" when omitted

📚 References

🔬 Testing

Unit test added in test/tools/auth0/handlers/clients.tests.js: should allow valid session_transfer delegation property in client — verifies the delegation config is
correctly passed through to the Management API on client create.

Manual end-to-end test against a tenant with the Custom Token Exchange Delegation feature flag enabled:

1. Added session_transfer.delegation.allow_delegated_access: true and enforce_device_binding: ip to a regular_web client config
2. Ran a0deploy import - Management API accepted the properties and returned 200
3. Verified the properties were persisted on the client via the Management API

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.19%. Comparing base (6701e54) to head (26d9eec).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1406   +/-   ##
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  Coverage   80.19%   80.19%           
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  Files         153      153           
  Lines        7119     7119           
  Branches     1573     1573           
=======================================
  Hits         5709     5709           
  Misses        760      760           
  Partials      650      650           

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