bug: fixing the endpoint msg string causing model in pending state

[Vishvajeet590]

What

Fix Postgres invalid byte sequence for encoding "UTF8" (SQLSTATE 22021) error when saving a version endpoint's deployment message.

Why

When a deployment fails, the Kubernetes error text (which often contains multi-byte box-drawing chars like ─ = 0xe2 0x94 0x80) is stored in version_endpoints.message. sanitizeEndpoint truncated it to maxMessageChar by byte slicing, which could cut a multi-byte character in half, leaving an invalid trailing sequence (e.g. 0xe2 0x94). Postgres then rejected the write, so the endpoint status/message never updated:

Error example

merlin {"level":"error","ts":1783331067.766427,"caller":"work/model_service_deployment.go:164","msg":"unable to update endpoint status for model: external-demo, version: 16, reason: ERROR: invalid byte sequence for encoding \"UTF8\": 0xe2 0x94 (SQLSTATE 22021)","stacktrace":"github.com/caraml-dev/merlin/queue/work.(*ModelServiceDeployment).Deploy.func1\n\t/src/api/queue/work/model_service_deployment.go:164\ngithub.com/caraml-dev/merlin/queue/work.(*ModelServiceDeployment).Deploy\n\t/src/api/queue/work/model_service_deployment.go:189\ngithub.com/caraml-dev/merlin/queue.(*worker).processJob\n\t/src/api/queue/worker.go:81"}

[anantadwi13]

lgtm. looks like the unit tests are already on the main branch 👀
b0ffd2f