Multiple Director Bug Fixes

[patrickbrophy]

This PR addresses issue #2369.

The following key changes were made:

1. Implemented nil checks in advertisement handling, specifically within updateInternalDirectorCache and IsDirectorAdFromSelf. This resolves the SIGSEGV and nil pointer dereference panics that occurred when processing nil director ads, a core problem noted in the issue.

2. All service and director advertisements are now wrapped in a consistent forwardAd struct before being propagated to other directors. This ensures uniform processing across the federation.

3. Directors now track the originator of incoming service ads and will not forward them back to the sender. This crucial change prevents advertisement loops, which were causing instability and timeouts.

4. Fixed a bug in updateInternalDirectorCache where updating a director's information would inadvertently discard existing data. The cache update now correctly modifies the entry in-place, preserving data integrity and ensuring each director maintains an accurate view of its peers.

[bbockelm]

A few small items and a request for a unit test (since it looks like there's one big broken piece that predated this PR).

[h2zh]

When two Directors are enabled in local dev environment, the Director Self Test on both Directors are flaky (see the below logs and screenshot).

DEBUG[2025-07-07T22:11:47Z] Starting a director test cycle for Cache server 88386cd92f0a at https://88386cd92f0a:8442 
DEBUG[2025-07-07T22:11:47Z] Director file transfer test cycle succeeded at 2025-07-07T22:11:47Z for Cache server with URL at https://88386cd92f0a:8442 
DEBUG[2025-07-07T22:11:47Z] Signing token with key id: at4Rza8YjVaviIxNlSFsDBux3pF2SsbTyxPsV9A9Pak 
DEBUG[2025-07-07T22:11:47Z] Director is sending Cache server test result to https://88386cd92f0a:8449/api/v1.0/cache/directorTest 
DEBUG[2025-07-07T22:11:48Z] Starting a director test cycle for Origin server 88386cd92f0a-Origin at https://88386cd92f0a:8443 
DEBUG[2025-07-07T22:11:48Z] Signing token with key id: at4Rza8YjVaviIxNlSFsDBux3pF2SsbTyxPsV9A9Pak 
WARNING[2025-07-07T22:11:48Z] Director file transfer test cycle failed for  Origin  server:  https://88386cd92f0a:8443   Test file transfer failed during upload: Error response 423 from test file upload: 423 Unknown 
DEBUG[2025-07-07T22:11:48Z] Signing token with key id: at4Rza8YjVaviIxNlSFsDBux3pF2SsbTyxPsV9A9Pak 
DEBUG[2025-07-07T22:11:48Z] Director is sending Origin server test result to https://88386cd92f0a:8447/api/v1.0/origin/directorTest 
WARNING[2025-07-07T22:11:48Z] Failed to report director test result to Origin server at https://88386cd92f0a:8447: error response 403 from reporting director test: {"status":"error","msg":"Failed to verify the token: Cannot verify token: Cannot verify token with federation issuer:  Failed to get federation's public JWKS: cached object is not a Set (was \u003cnil\u003e)\n"} 

[h2zh]

Neat and clever PR that fixes multiple bugs! It’d be nice to have a concise writeup with diagram. Also the next step could be adding prometheus metrics.

[patrickbrophy]

Looks like Mac TestStatMemory is continuing to be flaky

[jhiemstrawisc]

Using super powers to merge, since review of this PR was handed off from BrianB to Howard with a dangling request for changes.