Starting the constructor for ParametersContext.

src/renderer/parameters_context.rs

@@ -30,7 +30,17 @@ impl<'a> ParametersContext<'a> {
         breadcrumbs: Option<&BreadcrumbTree>,
         params: &Vec<KVPair>,
     ) -> Self {
-        todo!()
+        // If the parameter is a Path, then we resolve it immediately
+        // to a context element because those are resolved using the
+        // breadcrumbs at the time of assignment.
+        //
+        // If the parameter is a template (for example `foo="{bar}"`)
+        // then those are resolved at the time of access rather than
+        // the time of assignment, so we leave them into their
+        // original IntoContextElement state.
+        ParametersContext {
+            params: HashMap::new(),
+        }
     }
 }