Misskey metadata support

This commit implements misskey metadata support and corresponding test
for From<MskyMeta> implementation

Also, it is good to note that, Misskey does not return 404 but 200 OK
when they poked at nonexistant endpoint, so the implementation should
handle for invalid json case

src/error.rs

@@ -30,6 +30,10 @@ impl Error {
     pub(crate) fn is_gone(&self) -> bool {
         matches!(self.kind, ErrorKind::Status(_, StatusCode::GONE))
     }
+
+    pub(crate) fn is_malformed_json(&self) -> bool {
+        matches!(self.kind, ErrorKind::Json(_))
+    }
 }
 
 impl std::fmt::Debug for Error {

src/requests.rs

@@ -257,6 +257,14 @@ impl Requests {
         self.do_fetch(url, "application/json").await
     }
 
+    #[tracing::instrument(name = "Fetch Json", skip(self), fields(signing_string))]
+    pub(crate) async fn fetch_json_msky<T>(&self, url: &str) -> Result<T, Error>
+    where
+        T: serde::de::DeserializeOwned,
+    {
+        self.do_fetch_msky(url, "application/json").await
+    }
+
     #[tracing::instrument(name = "Fetch Activity+Json", skip(self), fields(signing_string))]
     pub(crate) async fn fetch<T>(&self, url: &str) -> Result<T, Error>
     where
@@ -266,6 +274,20 @@ impl Requests {
     }
 
     async fn do_fetch<T>(&self, url: &str, accept: &str) -> Result<T, Error>
+    where
+        T: serde::de::DeserializeOwned,
+    {
+        self.do_fetch_inner(url, accept, false).await
+    }
+
+    async fn do_fetch_msky<T>(&self, url: &str, accept: &str) -> Result<T, Error>
+    where
+        T: serde::de::DeserializeOwned,
+    {
+        self.do_fetch_inner(url, accept, true).await
+    }
+
+    async fn do_fetch_inner<T>(&self, url: &str, accept: &str, use_post: bool) -> Result<T, Error>
     where
         T: serde::de::DeserializeOwned,
     {
@@ -279,8 +301,11 @@ impl Requests {
         let span = tracing::Span::current();
 
         let client: Client = self.client.borrow().clone();
-        let res = client
+        let client_req = match use_post {
-            .get(url)
+            true => client.post(url),
+            false => client.get(url),
+        };
+        let res = client_req
             .insert_header(("Accept", accept))
             .insert_header(Date(SystemTime::now().into()))
             .signature(