server: add ability to view inline image attachments

server/src/error.rs

@@ -1,3 +1,4 @@
+use mailparse::MailParseError;
 use thiserror::Error;
 
 #[derive(Error, Debug)]
@@ -6,4 +7,10 @@ pub enum ServerError {
     NotmuchError(#[from] notmuch::NotmuchError),
     #[error("flatten")]
     FlattenError,
+    #[error("mail parse error")]
+    MailParseError(#[from] MailParseError),
+    #[error("IO error")]
+    IoError(#[from] std::io::Error),
+    #[error("attachement not found")]
+    PartNotFound,
 }