Switch from axum to axum-core and http

This will hopefully keep dependency churn lower.

src/axum.rs

@@ -1,14 +1,25 @@
-use axum::{
-    http::StatusCode,
-    response::{Html, IntoResponse},
-};
+use axum_core::response::IntoResponse;
+use http::{header, HeaderValue, StatusCode};
 
 use crate::{Document, Render};
 
+// https://github.com/hyperium/mime/blob/ce5062d216bf757a0ed3fc70f0fe255d1c8d74ae/src/lib.rs#L753
+const TEXT_HTML_UTF_8: &str = "text/html; charset=utf-8";
+
 impl IntoResponse for Document {
-    fn into_response(self) -> axum::response::Response {
+    fn into_response(self) -> axum_core::response::Response {
         match self.render_to_string() {
-            Ok(html) => Html(html).into_response(),
+            // Keeping dependency churn low by manually reimplementing
+            // https://github.com/tokio-rs/axum/blob/b5a01092216d0fa5ab950cbd7030ebcc925ceb33/axum/src/response/mod.rs#L40-L54
+            Ok(html) => (
+                [(
+                    header::CONTENT_TYPE,
+                    HeaderValue::from_static(TEXT_HTML_UTF_8),
+                )],
+                html,
+            )
+                .into_response(),
+
             Err(err) => (StatusCode::INTERNAL_SERVER_ERROR, err.to_string()).into_response(),
         }
     }