feat: add support for IMAP METADATA

src/imap/capabilities.rs

@@ -21,6 +21,10 @@ pub(crate) struct Capabilities {
     /// <https://tools.ietf.org/html/rfc7162>
     pub can_condstore: bool,
 
+    /// True if the server has METADATA capability as defined in
+    /// <https://tools.ietf.org/html/rfc5464>
+    pub can_metadata: bool,
+
     /// Server ID if the server supports ID capability.
     pub server_id: Option<HashMap<String, String>>,
 }

src/imap/client.rs

@@ -59,6 +59,7 @@ async fn determine_capabilities(
         can_move: caps.has_str("MOVE"),
         can_check_quota: caps.has_str("QUOTA"),
         can_condstore: caps.has_str("CONDSTORE"),
+        can_metadata: caps.has_str("METADATA"),
         server_id,
     };
     Ok(capabilities)

src/imap/session.rs

@@ -64,4 +64,8 @@ impl Session {
     pub fn can_condstore(&self) -> bool {
         self.capabilities.can_condstore
     }
+
+    pub fn can_metadata(&self) -> bool {
+        self.capabilities.can_metadata
+    }
 }