Starting a struct for what will be passed as the context into dust.

src/blog_post/mod.rs

@@ -1,2 +1,3 @@
 mod definition;
+mod render_context;
 pub(crate) use definition::BlogPost;

src/blog_post/render_context.rs

@@ -0,0 +1,8 @@
+use serde::Serialize;
+
+#[derive(Debug, Serialize)]
+#[serde(tag = "type")]
+#[serde(rename = "blog_post")]
+pub(crate) struct RenderBlogPost {
+    id: String,
+}