Add msg:set_data()

This method allows replacing the message payload arbitrarily.
This is a building block for more advanced and convenient
modification operations.

refs: https://github.com/KumoCorp/kumomta/issues/117
refs: https://github.com/KumoCorp/kumomta/issues/120

crates/message/src/message.rs

@@ -915,6 +915,10 @@ impl UserData for Message {
             let data = this.get_data();
             lua.create_string(&*data)
         });
+        methods.add_method("set_data", move |_lua, this, data: mlua::String| {
+            this.assign_data(data.as_bytes().to_vec());
+            Ok(())
+        });
         methods.add_method("id", move |_, this, _: ()| Ok(this.id().to_string()));
         methods.add_method("sender", move |_, this, _: ()| {
             Ok(this.sender().map_err(any_err)?)

docs/reference/message/get_data.md

@@ -2,3 +2,5 @@
 
 Returns the message body/data as a string.
 
+See also:
+* [msg:set_data()](set_data.md)

docs/reference/message/set_data.md

@@ -0,0 +1,11 @@
+# `message:set_data(payload)`
+
+{{since('dev')}}
+
+Replaces the message body/data completely.
+It is your responsibility to ensure that the content is well-formed, has
+canonical CRLF line endings, and uses appropriate transfer-encoding, otherwise
+the system will misbehave when delivering the message.
+
+See also:
+* [msg:get_data()](get_data.md)