feat: policy engine (#450)

* feat: policy engine

* fix: cargo fmt

* fix: resolve issues with miri

bindings/python/src/content.rs

@@ -16,7 +16,9 @@ impl PyZenDecisionContent {
     pub fn new(data: &str) -> PyResult<Self> {
         let mut content: DecisionContent =
             serde_json::from_str(data).context("Failed to parse JSON")?;
-        content.compile();
+        if let DecisionContent::Graph(g) = &mut content {
+            g.compile();
+        }
         Ok(Self(Arc::new(content)))
     }
 }

bindings/python/src/engine.rs

@@ -168,13 +168,17 @@ impl PyZenEngine {
     }
 
     pub fn create_decision(&self, content: PyZenDecisionContentJson) -> PyResult<PyZenDecision> {
-        let decision = self.engine.create_decision(content.0 .0);
+        let decision = self
+            .engine
+            .create_decision(content.0 .0)
+            .map_err(|e| anyhow!(e.to_string()))?;
         Ok(PyZenDecision::from(decision))
     }
 
     pub fn get_decision<'py>(&'py self, _py: Python<'py>, key: &str) -> PyResult<PyZenDecision> {
         let decision = block_on(self.engine.get_decision(key))
-            .context("Failed to find decision with given key")?;
+            .context("Failed to find decision with given key")?
+            .map_err(|e| anyhow!(e.to_string()))?;
 
         Ok(PyZenDecision::from(decision))
     }