Minor cleanup of Viewtype

Provide checking for attachment as a method and move it to the message
module.  The method is a lot easier to read and have correct
expectations about.

src/constants.rs

@@ -231,82 +231,6 @@ pub const DC_FOLDERS_CONFIGURED_VERSION: i32 = 3;
 // can be overwritten by the setting `max_smtp_rcpt_to` in provider-db.
 pub const DEFAULT_MAX_SMTP_RCPT_TO: usize = 50;
 
-#[derive(
-    Debug,
-    Display,
-    Clone,
-    Copy,
-    PartialEq,
-    Eq,
-    FromPrimitive,
-    ToPrimitive,
-    FromSql,
-    ToSql,
-    Serialize,
-    Deserialize,
-)]
-#[repr(u32)]
-pub enum Viewtype {
-    Unknown = 0,
-
-    /// Text message.
-    /// The text of the message is set using dc_msg_set_text()
-    /// and retrieved with dc_msg_get_text().
-    Text = 10,
-
-    /// Image message.
-    /// If the image is an animated GIF, the type DC_MSG_GIF should be used.
-    /// File, width and height are set via dc_msg_set_file(), dc_msg_set_dimension
-    /// and retrieved via dc_msg_set_file(), dc_msg_set_dimension().
-    Image = 20,
-
-    /// Animated GIF message.
-    /// File, width and height are set via dc_msg_set_file(), dc_msg_set_dimension()
-    /// and retrieved via dc_msg_get_file(), dc_msg_get_width(), dc_msg_get_height().
-    Gif = 21,
-
-    /// Message containing a sticker, similar to image.
-    /// If possible, the ui should display the image without borders in a transparent way.
-    /// A click on a sticker will offer to install the sticker set in some future.
-    Sticker = 23,
-
-    /// Message containing an Audio file.
-    /// File and duration are set via dc_msg_set_file(), dc_msg_set_duration()
-    /// and retrieved via dc_msg_get_file(), dc_msg_get_duration().
-    Audio = 40,
-
-    /// A voice message that was directly recorded by the user.
-    /// For all other audio messages, the type #DC_MSG_AUDIO should be used.
-    /// File and duration are set via dc_msg_set_file(), dc_msg_set_duration()
-    /// and retrieved via dc_msg_get_file(), dc_msg_get_duration()
-    Voice = 41,
-
-    /// Video messages.
-    /// File, width, height and durarion
-    /// are set via dc_msg_set_file(), dc_msg_set_dimension(), dc_msg_set_duration()
-    /// and retrieved via
-    /// dc_msg_get_file(), dc_msg_get_width(),
-    /// dc_msg_get_height(), dc_msg_get_duration().
-    Video = 50,
-
-    /// Message containing any file, eg. a PDF.
-    /// The file is set via dc_msg_set_file()
-    /// and retrieved via dc_msg_get_file().
-    File = 60,
-
-    /// Message is an invitation to a videochat.
-    VideochatInvitation = 70,
-
-    /// Message is an webxdc instance.
-    Webxdc = 80,
-}
-
-impl Default for Viewtype {
-    fn default() -> Self {
-        Viewtype::Unknown
-    }
-}
-
 pub const DC_JOB_DELETE_MSG_ON_IMAP: i32 = 110;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, FromPrimitive, ToPrimitive)]
@@ -318,33 +242,9 @@ pub enum KeyType {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use num_traits::FromPrimitive;
 
-    #[test]
-    fn test_derive_display_works_as_expected() {
-        assert_eq!(format!("{}", Viewtype::Audio), "Audio");
-    }
-
-    #[test]
-    fn test_viewtype_values() {
-        // values may be written to disk and must not change
-        assert_eq!(Viewtype::Unknown, Viewtype::default());
-        assert_eq!(Viewtype::Unknown, Viewtype::from_i32(0).unwrap());
-        assert_eq!(Viewtype::Text, Viewtype::from_i32(10).unwrap());
-        assert_eq!(Viewtype::Image, Viewtype::from_i32(20).unwrap());
-        assert_eq!(Viewtype::Gif, Viewtype::from_i32(21).unwrap());
-        assert_eq!(Viewtype::Sticker, Viewtype::from_i32(23).unwrap());
-        assert_eq!(Viewtype::Audio, Viewtype::from_i32(40).unwrap());
-        assert_eq!(Viewtype::Voice, Viewtype::from_i32(41).unwrap());
-        assert_eq!(Viewtype::Video, Viewtype::from_i32(50).unwrap());
-        assert_eq!(Viewtype::File, Viewtype::from_i32(60).unwrap());
-        assert_eq!(
-            Viewtype::VideochatInvitation,
-            Viewtype::from_i32(70).unwrap()
-        );
-        assert_eq!(Viewtype::Webxdc, Viewtype::from_i32(80).unwrap());
-    }
+    use super::*;
 
     #[test]
     fn test_chattype_values() {