feat(dataverse): implement vc proof parsing

contracts/okp4-dataverse/src/did/crypto.rs

@@ -0,0 +1,35 @@
+use crate::did::consts::RDF_TYPE;
+use crate::ContractError;
+use itertools::Itertools;
+use okp4_rdf::dataset::{Dataset, QuadIterator};
+use rio_api::model::Term;
+
+pub struct Proof<'a> {
+    type_: String,
+    inner: Dataset<'a>,
+}
+
+impl<'a> TryFrom<Dataset<'a>> for Proof<'a> {
+    type Error = ContractError;
+
+    fn try_from(dataset: Dataset<'a>) -> Result<Self, Self::Error> {
+        Ok(Self {
+            type_: dataset
+                .match_pattern(None, Some(RDF_TYPE), None, None)
+                .objects()
+                .exactly_one()
+                .map_err(|_| {
+                    ContractError::InvalidCredential(
+                        "Credential proof can must have only one type".to_string(),
+                    )
+                })
+                .and_then(|o| match o {
+                    Term::NamedNode(n) => Ok(n.iri.to_string()),
+                    _ => Err(ContractError::InvalidCredential(
+                        "Credential proof type must be a named node".to_string(),
+                    )),
+                })?,
+            inner: dataset,
+        })
+    }
+}