feat: add secret creation with modelconfig in REST API

[supreme-gg-gg]

No description provided.

[Copilot]

Pull request overview

Adds support for creating/updating “companion” Kubernetes Secrets as part of the ModelConfig REST create/update flows, enabling clients to submit secret material alongside a ModelConfig spec.

Changes:

• Extend REST API request payloads to accept secrets (name/key/value/type) on create/update.
• Implement validation + create/update logic for companion Secrets in the ModelConfig HTTP handler.
• Add handler tests covering successful companion secret creation/update and invalid secret names.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
ui/src/types/index.ts	Adds SecretMaterial and extends ModelConfig create/update request types with optional secrets.
go/api/httpapi/types.go	Adds SecretMaterial + secrets fields to ModelConfig create/update API request structs.
go/core/internal/httpserver/handlers/modelconfig.go	Validates secret material and creates/updates companion Secrets during ModelConfig create/update.
go/core/internal/httpserver/handlers/modelconfig_test.go	Adds tests for companion secret behavior and validation.

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[EItanya]

I agree with Copilot's comments here. I think we should be careful about the secrets we edit/overwrite here. Since these are implicitly managed by kagent it may even be worth creating the ModelConfig first, and then using an OwnerReference to make sure these secrets are cleaned up when the ModelConfig is deleted.

[EItanya]

Why do we need to specify type, let's keep it Opaque for now and add it if it becomes necessary later?

[supreme-gg-gg]

Yes I totally agree with that, I've address copilot's reviews as well. Now modelconfig is created first then the secret, on updates it checks that the secret is owned by the modelconfig, and deleting the modelconfig deletes the secrets as well (due to owner reference)