[PATCH proxmox 1/1] sendmail: add additional header map

[Nicolas Frey <n.frey@proxmox.com>]

with corresponding methods to add them.

this does not check for duplicates for the ones already set by other
fields/defaults (e.g. To, From, Content-Type, etc.)

Signed-off-by: Nicolas Frey <n.frey@proxmox.com>
---
 proxmox-sendmail/src/lib.rs | 47 +++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/proxmox-sendmail/src/lib.rs b/proxmox-sendmail/src/lib.rs
index db751305..355a84c2 100644
--- a/proxmox-sendmail/src/lib.rs
+++ b/proxmox-sendmail/src/lib.rs
@@ -3,6 +3,7 @@
 //! and alternative html parts to one or multiple receivers via ``sendmail``.
 //!
 
+use std::collections::HashMap;
 use std::io::Write;
 use std::process::{Command, Stdio};
 
@@ -247,6 +248,7 @@ pub struct Mail<'a> {
     attachments: Vec<Attachment<'a>>,
     mask_participants: bool,
     noreply: Option<Recipient>,
+    additional_headers: HashMap<String, String>,
 }
 
 impl<'a> Mail<'a> {
@@ -265,6 +267,7 @@ impl<'a> Mail<'a> {
             attachments: Vec::new(),
             mask_participants: true,
             noreply: None,
+            additional_headers: HashMap::new(),
         }
     }
 
@@ -393,6 +396,20 @@ impl<'a> Mail<'a> {
         self
     }
 
+    /// Set an arbitrary header to be sent in addition to the default ones already set up by other
+    /// methods.
+    pub fn set_header<S: ToString>(&mut self, name: S, body: S) {
+        self.additional_headers
+            .insert(name.to_string(), body.to_string());
+    }
+
+    /// Builder-style method to set an arbitrary header in addition to the default ones already
+    /// set up by other methods.
+    pub fn with_header<S: ToString>(mut self, name: S, body: S) -> Self {
+        self.set_header(name, body);
+        self
+    }
+
     /// Sends the email. This will fail if no recipients have been added.
     ///
     /// Note: An `Auto-Submitted: auto-generated` header is added to avoid triggering OOO and
@@ -584,6 +601,11 @@ impl<'a> Mail<'a> {
         let rfc2822_date = proxmox_time::epoch_to_rfc2822(now)
             .with_context(|| "could not convert epoch to rfc2822 date")?;
         writeln!(header, "Date: {rfc2822_date}")?;
+
+        for (name, body) in &self.additional_headers {
+            writeln!(header, "{name}: {body}")?;
+        }
+
         header.push_str("Auto-Submitted: auto-generated;\n");
 
         Ok(header)
@@ -681,6 +703,31 @@ mod test {
         assert!(result.is_err());
     }
 
+    #[test]
+    fn additional_headers() {
+        let mail = Mail::new("Sender", "mail@example.com", "hi", "body")
+            .with_recipient_and_name("Jane Doe", "j.doe@example.com")
+            .with_header("Reply-To", "mail@example.com")
+            .with_header("CC", "cc1@example.com,cc2@example.com");
+        let body = mail.format_mail(0).expect("could not format mail");
+
+        assert_lines_equal_ignore_date(
+            &body,
+            r#"Subject: hi
+From: Sender <mail@example.com>
+To: Jane Doe <j.doe@example.com>
+Date: Thu, 01 Jan 1970 01:00:00 +0100
+Reply-To: mail@example.com
+CC: cc1@example.com,cc2@example.com
+Auto-Submitted: auto-generated;
+Content-Type: text/plain;
+	charset="UTF-8"
+Content-Transfer-Encoding: 7bit
+
+body"#,
+        )
+    }
+
     #[test]
     fn simple_ascii_text_mail() {
         let mail = Mail::new(
-- 
2.47.3