melib/notmuch: add sent_mailbox_path conf setting

Where to store sent e-mail in the filesystem.

docs/meli.conf.5

@@ -199,11 +199,19 @@ property to each of them.
 .It Ic library_file_path Ar Path
 Use an arbitrary location of libnotmuch by specifying its full filesystem path.
 .Pq Em optional
+.It Ic sent_mailbox_path Ar Path
+Where to store sent e-mail in the filesystem.
+Defaults to
+.Ic root_mailbox Ns
+\&.
+.Pq Em optional
 .El
 Example:
 .Bd -literal
 [accounts.notmuch]
+root_mailbox = "/path/to/notmuch/folder"
 format = "notmuch"
+sent_mailbox_path = "/path/to/notmuch/folder/Sent/cur"
 #library_file_path = "/opt/homebrew/lib/libnotmuch.5.dylib"
 \&...
   [accounts.notmuch.mailboxes]

melib/src/backends/notmuch.rs

@@ -490,6 +490,18 @@ impl NotmuchDb {
                 .set_kind(ErrorKind::Configuration));
             }
         }
+        let save_messages_to = if let Some(sent_path) = s.extra.get("sent_mailbox_path") {
+            if !Path::new(&sent_path).exists() || !Path::new(&sent_path).is_dir() {
+                return Err(MeliError::new(format!(
+                            "Notmuch `sent_mailbox_path` setting value `{}` for account {} does not exist or is not a directory.",
+                            &sent_path,
+                            s.name()
+                )).set_kind(ErrorKind::Configuration));
+            }
+            Some(Path::new(&sent_path).to_path_buf())
+        } else {
+            None
+        };
 
         let account_hash = {
             let mut hasher = DefaultHasher::new();
@@ -509,7 +521,7 @@ impl NotmuchDb {
             account_name: account_name.clone(),
             account_hash,
             event_consumer: event_consumer.clone(),
-            save_messages_to: None,
+            save_messages_to: save_messages_to.clone(),
         });
         Ok(Box::new(NotmuchDb {
             lib,
@@ -519,7 +531,7 @@ impl NotmuchDb {
             account_name,
             account_hash,
             event_consumer,
-            save_messages_to: None,
+            save_messages_to,
         }))
     }
 
@@ -571,6 +583,15 @@ impl NotmuchDb {
                 .set_kind(ErrorKind::Configuration));
             }
         }
+        if let Some(sent_path) = s.extra.remove("sent_mailbox_path") {
+            if !Path::new(&sent_path).exists() || !Path::new(&sent_path).is_dir() {
+                return Err(MeliError::new(format!(
+                            "Notmuch `sent_mailbox_path` setting value `{}` for account {} does not exist or is not a directory.",
+                            &sent_path,
+                            s.name()
+                )).set_kind(ErrorKind::Configuration));
+            }
+        }
         Ok(())
     }