[9.1?] Add secrets in DIRAC integration tests

[Robin-Van-de-Merghel]

BEGINRELEASENOTES

Please follow the template:
*Integration tests
NEW: Add pilot secrets into the CI

ENDRELEASENOTES

[Robin-Van-de-Merghel]

This PR serves as a POC for the pilot secret-exchange mechanism. We have two cases:

1. Pilot with a secret (vacuum case with secret-exchange: DiracX)
2. Pilot with a proxy (vacuum case with RegisterPilot: DIRAC)

With secret

Source: https://github.com/DIRACGrid/DIRAC/actions/runs/16797372818/job/47570725488?pr=8279#step:12:192

As expected we simulate a vacuum case: first exchange failed because the pilot is not registered, second exchange success because it's a vacuum registration.

Maybe I can add a test to show a classic secret-exchange without vacuum case

Then RegisterPilot is blocked because we are already registered through the secret-exchange: https://github.com/DIRACGrid/DIRAC/actions/runs/16797372818/job/47570725488?pr=8279#step:12:1880

Without secret

Source: https://github.com/DIRACGrid/DIRAC/actions/runs/16797372818/job/47570725469?pr=8279#step:12:185

As expected, continue without DiracX, tried to get the token but failed.

Then RegisterPilot is a success because we don't have a secret-exchange: https://github.com/DIRACGrid/DIRAC/actions/runs/16797372818/job/47570725469?pr=8279#step:12:1871

Refs

Linked to:

• Pilot auth: feat: Adding JWT support alongside X509 auth Pilot#248
• Pilot auth in DiracX: Adding pilot registrations and authentification (Router) diracx#421
• Pilot legacy adaptor in DIRAC: [9.0] feat: Migrating pilot client toward DiracX #8233