ref(debug): Improve debug printing for envelope items and cogs

[Dav1dde]

Before:

TRACE relay_server::processing::relay: processing item: SerializedAttachments { headers: EnvelopeHeaders { event_id: Some(EventId(51553901-8c9b-4260-a6f9-99572f1661ee)), meta: RequestMeta { dsn: http://47d312dddd454ad7bf611cea74884371:@127.0.0.1:60024/42, client: Some("raven-node/2.6.3"), version: 5, origin: None, remote_addr: Some(127.0.0.1), forwarded_for: "127.0.0.1", user_agent: Some("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"), client_hints: ClientHints { sec_ch_ua_platform: None, sec_ch_ua_platform_version: None, sec_ch_ua: None, sec_ch_ua_model: None }, no_cache: false, received_at: 2026-05-28T11:23:25.872050Z, signature: None, request_trust: Some(Untrusted) }, retention: None, downsampled_retention: None, sent_at: None, trace: None, required_features: [], other: {} }, attachments: [Item { headers: ItemHeaders { ty: Attachment, stored_key: None, routing_hint: None, rate_limited: false, source_quantities: None, inner: {Known(Length): ItemHeaderValue(Number(12)), Known(AttachmentType): ItemHeaderValue(String("event.attachment")), Known(Filename): ItemHeaderValue(String("foo.txt"))} }, payload: b"file content" }] } processor="relay_server::processing::attachments::AttachmentProcessor"

TRACE relay_server::services::cogs: recording measurement: CogsMeasurement { resource: Relay, feature: StandaloneAttachments, category: None, value: Time(97.417µs) }

TRACE relay_server::processing::relay: processing item: InvalidUnhandledItems { invalid_items: [Item { headers: ItemHeaders { ty: FormData, stored_key: None, routing_hint: None, rate_limited: false, source_quantities: None, inner: {Known(Length): ItemHeaderValue(Number(26)), Known(ContentType): ItemHeaderValue(String("text/plain"))} }, payload: b"\x08\0\0\0form_key\n\0\0\0form value" }] } processor="relay_server::processing::invalid::InvalidUnhandledProcessor"

After:

TRACE relay_server::processing::relay: processing item: SerializedAttachments { headers: {"event_id": 51553901-8c9b-4260-a6f9-99572f1661ee, "meta": {"dsn": http://6a877703d1b343b6a2d27ba97bd6fd88:@127.0.0.1:60949/42, "client": "raven-node/2.6.3", "version": 5, "remote_addr": 127.0.0.1, "forwarded_for": "127.0.0.1", "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36", "received_at": 2026-05-28T11:48:33.598095Z, "request_trust": Untrusted}}, attachments: [Item { headers: {"type": Attachment, Length: "12", AttachmentType: "event.attachment", Filename: "foo.txt"}, payload: b"file content" }] } processor="relay_server::processing::attachments::AttachmentProcessor"

TRACE relay_server::services::cogs: recording measurement: Relay@standalone_attachments=156.792µs

TRACE relay_server::processing::relay: processing item: InvalidUnhandledItems { invalid_items: [Item { headers: {"type": FormData, Length: "26", ContentType: "text/plain"}, payload: b"\x08\0\0\0form_key\n\0\0\0form value" }] } processor="relay_server::processing::invalid::InvalidUnhandledProcessor"

Makes log output in tests/local sessions a bit more digestible.

[cursor]

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