Merge #183: elip100: add missing AssetMetadata::new method

add54c8 elip100: add missing AssetMetadata::new method (Riccardo Casatta)

Pull request description:

  Missing from #182  otherwise there is no way to instantiate `AssetMetadata` and call `add_asset_metadata`

ACKs for top commit:
  apoelstra:
    ACK add54c8

Tree-SHA512: 1a5e935aa76a0f288d8ac1c0917ccf441991f32b830bab26c9b1146a3d462bfeac1caad1c3035f2f54669731bef779ea72d2cd27ff9d65b90c38f0253e4274b1

Author: apoelstra

src/pset/elip100.rs

@@ -76,6 +76,12 @@ fn prop_key(asset_id: &AssetId) -> ProprietaryKey {
 }
 
 impl AssetMetadata {
+
+    /// Create a new [`AssetMetadata`]
+    pub fn new(contract: String, issuance_prevout: OutPoint) -> Self {
+        Self { contract, issuance_prevout }
+    }
+
     /// Returns the contract as string containing a json
     pub fn contract(&self) -> &str {
         &self.contract