Add serialization of finalize flag (#68)

Add a function `flags` to serialize the `finalize` flag of an IssueAction to a byte.
This function will be used by the client.

src/issuance.rs

@@ -61,6 +61,23 @@ impl IssueAction {
         }
     }
 
+    /// Constructs a new `IssueAction`.
+    pub fn new_with_finalize(asset_desc: String, note: &Note, flags: u8) -> Option<Self> {
+        let finalize = match flags {
+            0b0000_0000 => false,
+            0b0000_0001 => true,
+            _ => return None,
+        };
+        Some(IssueAction {
+            asset_desc,
+            notes: NonEmpty {
+                head: *note,
+                tail: vec![],
+            },
+            finalize,
+        })
+    }
+
     /// Constructs an `IssueAction` from its constituent parts.
     pub fn from_parts(asset_desc: String, notes: NonEmpty<Note>, finalize: bool) -> Self {
         IssueAction {
@@ -134,6 +151,11 @@ impl IssueAction {
             .then(|| Ok((asset, AssetSupply::new(value_sum, self.is_finalized()))))
             .ok_or(IssueBundleIkMismatchAssetBase)?
     }
+
+    /// Serialize `finalize` flag to a byte
+    pub fn flags(&self) -> u8 {
+        self.finalize.then(|| 0b0000_0001).unwrap_or(0b0000_0000)
+    }
 }
 
 /// Defines the authorization type of an Issue bundle.
@@ -1272,6 +1294,23 @@ mod tests {
             WrongAssetDescSize
         );
     }
+
+    #[test]
+    fn test_finalize_flag_serialization() {
+        let mut rng = OsRng;
+        let (_, _, note) = Note::dummy(&mut rng, None, AssetBase::native());
+
+        let action =
+            IssueAction::new_with_finalize(String::from("Asset description"), &note, 0u8).unwrap();
+        assert_eq!(action.flags(), 0b0000_0000);
+
+        let action =
+            IssueAction::new_with_finalize(String::from("Asset description"), &note, 1u8).unwrap();
+        assert_eq!(action.flags(), 0b0000_0001);
+
+        let action = IssueAction::new_with_finalize(String::from("Asset description"), &note, 2u8);
+        assert!(action.is_none());
+    }
 }
 
 /// Generators for property testing.