begin documenting some functions and align error messages

src/entries.rs

@@ -0,0 +1,11 @@
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+
+#[derive(Serialize, Deserialize, Default, Clone)]
+pub struct EntryDeclaration {
+    pub title: String,
+    #[serde(default)]
+    pub actions: Vec<String>,
+    #[serde(default)]
+    pub values: BTreeMap<String, String>,
+}