Set MSRV to 1.81

This will allow the CI system to ensure changes are backwards
compatible.

The version was chosen using `cargo msrv`.

Change-type: patch

Author: pipex

Cargo.toml

@@ -2,6 +2,7 @@
 name = "mahler"
 version = "0.19.4"
 edition = "2021"
+rust-version = "1.81"
 description = "An automated job orchestration library that builds and executes dynamic workflows"
 homepage = "https://github.com/balena-io-modules/mahler-rs"
 keywords = ["job", "orchestration", "workflow", "library"]

src/extract/view.rs

@@ -393,7 +393,7 @@ mod tests {
 
         assert_eq!(view.as_ref(), None);
 
-        let value = view.get_or_insert_default();
+        let value = view.get_or_insert(0);
         *value = 3;
 
         // Get the list changes to the view