Function server_fail_value_from_backend 

pub fn server_fail_value_from_backend<E: Display + ?Sized>(_err: &E) -> Value

Construct the per-id serverFail Value used inside the notCreated/notUpdated/notDestroyed maps of /set responses (bd:JMAP-ic0j.68), without echoing the backend error’s Display output onto the wire.

This is the Value-shaped sibling of server_fail_from_backend. The handler-layer helper returns a JmapError which is only useful where the entire method invocation fails. Per-id /set failures are expressed as a serde_json::Value keyed under each failing id in notCreated / notUpdated / notDestroyed; the existing JmapError-shaped helper does not fit those sites, so each crate previously hand-rolled json!({ "type": "serverFail", "description": e.to_string() }) — every one of which leaks the backend error’s Display onto the wire, in direct violation of the JmapBackend::Error Display MUST-NOT contract.

The err parameter is intentionally discarded (bd:JMAP-jfia.22), matching the contract on server_fail_from_backend. It exists only to keep the call site ergonomic — the function never reads it, logs it, or stashes it. Callers that want their backend error visible in operator logs MUST log it explicitly at the call site before invoking this helper.

The function is generic over any Display so it applies uniformly to JmapBackend::Error, BackendSetError::Other, BackendChangesError::Other, and any extension-trait-specific error envelope. It also accepts the &String shape produced by some legacy helpers that flattened a backend error to String before propagating.

Use at every per-id /set serverFail site

Replace:

json!({ "type": "serverFail", "description": e.to_string() })

with:

server_fail_value_from_backend(&e)