Import upstream v0.16.23, stripped

Upstream commit: 9d1c75ab68435e4417337f768291e5f947686203
Enterprise-only files removed or emptied: 63
Enterprise-only snippets removed: 118 in 50 files
Dangling module declarations removed: 5
Edits turning enterprise off: 25
Third-party code: 14 files, 0 not in THIRD-PARTY.md
Verification: clean

One snippet more than v0.16.22, in crates/common/src/auth/authentication.rs
(3, was 2).

crates/email/src/message/delivery.rs

@@ -17,6 +17,8 @@ use std::{borrow::Cow, future::Future};
 use store::ahash::AHashMap;
 use types::blob_hash::BlobHash;
 
+pub const ORCPT_ADDR_TYPE: &str = "rfc822;";
+
 #[derive(Debug)]
 pub struct IngestMessage {
     pub sender_address: String,
@@ -35,6 +37,12 @@ pub struct IngestRecipient {
 }
 
 impl IngestRecipient {
+    pub fn orcpt_parameter(&self) -> Option<String> {
+        self.orcpt
+            .as_deref()
+            .map(|orcpt| format!("{ORCPT_ADDR_TYPE}{orcpt}"))
+    }
+
     pub fn is_spam(&self) -> bool {
         self.spam_percentage
             .is_some_and(|percentage| percentage >= 50)