fix(cloud-functions): accept per-model routing expressions

[along-2017]

TL;DR

Function owners can persist per-model routing expressions such as
pulsar;seed=stable-a;n=2 in llmConfig.routingMethod. The API now validates
format only and normalizes the algorithm token to the router's canonical
spelling; the router stays the semantic authority and rejects invalid
expressions at request time.

Additional Details

The routing method allow-list is replaced by grammar validation (a profile of
RFC 8941 Item with Parameters): algorithm token, optional ;key=value
parameters, values as integer, decimal, token, or quoted string, no commas, no
duplicate keys, 1024-byte cap. Well-formed but semantically wrong expressions
persist by design, so the validator and the router cannot drift on semantics.
Write-time normalization (lowercase, underscore to hyphen, alias map) converges
newly persisted values on canonical algorithm names; the deprecated
multiregion aliases normalize to their replacements.

Do not merge until the router-side expression support has rolled out:
persisted expressions reach the router verbatim, and routers without the
parser reject those models' requests. Sequencing is tracked on the parent
issue.

For the Reviewer

The grammar and its profile rules are the review core:
LlmConfigValidator.validateAndNormalizeRoutingMethod and its parameterized
test table. The two call sites now persist the returned normalized value.

For QA

bazel test //src/control-plane-services/cloud-functions/nvcf-core:tests:
LlmConfigValidatorTest passes fully (all parameterized cases). The target
overall fails locally without Docker because unrelated Testcontainers
integration tests need it; CI provides Docker.

Issues

Relates to #536

Checklist

• I am familiar with the Contributing Guidelines.
• I have signed off my commits for Developer Certificate of Origin (DCO) compliance.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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🛡️ CodeQL Analysis

🚨 Found 11 issue(s)

Severity Breakdown:

• 🔴 Errors: 0
• 🟡 Warnings: 0
• 🔵 Notes: 0

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_{🕐 Last updated: 2026-08-31 20:53:51 UTC | Commit: d22207d}