Legal holds, step 3: deleted items in a held account are kept

Every way of deleting mail (JMAP, IMAP EXPUNGE, POP3, mailbox removal,
Trash emptying) and Sieve scripts, events, contacts and files now asks
how the account's deletions are kept: a hold keeps them with no expiry
(archivedUntil 9999-12-31), even with undelete off; otherwise undelete's
period applies as before (LH-4).

A hold's date range decides by the item's own date (LH-3). Mail is noted
as held at deletion and settled when it's archived, once its received
date is known; outside the range it gets undelete's deadline or isn't
kept. Events go by their start, with a day's slack for time zones;
recurring events, contacts, files and scripts are held whole.

A groupware item's note now stays until its archive succeeds, and a
failure retries the task instead of being logged and lost (LH-5).

crates/features/src/undelete/email.rs

@@ -12,9 +12,12 @@
 //! is made if archiving is on, fixing the deadline then. When the data is
 //! finally removed, a noted message becomes an archived item.
 
-use crate::undelete::{
-    data::{self, EmailNote, Extra},
-    records,
+use crate::{
+    hold::Keeping,
+    undelete::{
+        data::{self, EmailNote, Extra},
+        records,
+    },
 };
 use registry::{
     schema::structs::{ArchivedEmail, ArchivedItem},
@@ -26,10 +29,12 @@ use store::{
 };
 use types::{blob::BlobId, blob_hash::BlobHash};
 
-/// Notes a deleted message, when archiving is on (`retention` seconds).
+/// Notes a deleted message, when anything keeps it: undelete, or a legal
+/// hold on the account (LH-4). A held note keeps it until it's archived,
+/// when its received date says whether the hold's range covers it.
 pub fn note(
     batch: &mut BatchBuilder,
-    retention: u64,
+    keeping: &Keeping,
     account_id: u32,
     document_id: u32,
     size: u64,
@@ -37,16 +42,23 @@ pub fn note(
     keywords: Vec<String>,
 ) -> trc::Result<()> {
     let archived_at = now();
+    // Held until the date is known; the undelete deadline otherwise
+    let otherwise_until = keeping.until(archived_at, false);
+    let Some(archived_until) = keeping.until(archived_at, keeping.is_held()) else {
+        return Ok(());
+    };
     data::note_email(
         batch,
         account_id,
         document_id,
         &EmailNote {
             archived_at,
-            archived_until: archived_at + retention,
+            archived_until,
             size,
             mailboxes,
             keywords,
+            held_ranges: keeping.ranges.clone(),
+            otherwise_until: if keeping.is_held() { otherwise_until } else { None },
         },
     )
 }
@@ -78,9 +90,27 @@ pub async fn archive(
     document_id: u32,
     summary: Summary<'_>,
 ) -> trc::Result<bool> {
-    let Some(note) = data::email_note(data, account_id, document_id).await? else {
+    let Some(mut note) = data::email_note(data, account_id, document_id).await? else {
         return Ok(false);
     };
+    // LH-3: a held note's range decides now that the date is known; outside
+    // it, undelete's deadline, or nothing kept at all
+    if !note.held_ranges.is_empty() {
+        let keeping = Keeping {
+            retention: None,
+            ranges: std::mem::take(&mut note.held_ranges),
+        };
+        if !keeping.covers(Some(summary.received_at)) {
+            match note.otherwise_until {
+                Some(until) => note.archived_until = until,
+                None => {
+                    let mut batch = BatchBuilder::new();
+                    data::clear_email_note(&mut batch, account_id, document_id);
+                    return data.write(batch.build_all()).await.map(|_| false);
+                }
+            }
+        }
+    }
     let item = ArchivedItem::Email(ArchivedEmail {
         from: summary.from.unwrap_or_default().to_string(),
         subject: summary.subject.unwrap_or_default().to_string(),