feat: detect XCHATMAIL capability and expose it as is_chatmail config

src/imap/capabilities.rs

@@ -32,6 +32,14 @@ pub(crate) struct Capabilities {
     /// This is supported by <https://github.com/deltachat/chatmail>
     pub can_push: bool,
 
+    /// True if the server has an XCHATMAIL capability
+    /// indicating that it is a <https://github.com/deltachat/chatmail> server.
+    ///
+    /// This can be used to hide some advanced settings in the UI
+    /// that are only interesting for normal email accounts,
+    /// e.g. the ability to move messages to Delta Chat folder.
+    pub is_chatmail: bool,
+
     /// Server ID if the server supports ID capability.
     pub server_id: Option<HashMap<String, String>>,
 }

src/imap/client.rs

@@ -61,6 +61,7 @@ async fn determine_capabilities(
         can_condstore: caps.has_str("CONDSTORE"),
         can_metadata: caps.has_str("METADATA"),
         can_push: caps.has_str("XDELTAPUSH"),
+        is_chatmail: caps.has_str("XCHATMAIL"),
         server_id,
     };
     Ok(capabilities)

src/imap/session.rs

@@ -94,6 +94,11 @@ impl Session {
         self.capabilities.can_push
     }
 
+    // Returns true if IMAP server has `XCHATMAIL` capability.
+    pub fn is_chatmail(&self) -> bool {
+        self.capabilities.is_chatmail
+    }
+
     /// Returns the names of all folders on the IMAP server.
     pub async fn list_folders(&mut self) -> Result<Vec<async_imap::types::Name>> {
         let list = self.list(Some(""), Some("*")).await?.try_collect().await?;