Add insert_user_agent option in composing

Add option for automatically inserting a 'User-Agent' header in new
drafts.

meli.conf.5

@@ -384,6 +384,11 @@ Editor must be xterm compliant.
 Set format=flowed [RFC3676] in text/plain attachments.
 .\" default value
 .Pq Em true
+.It Ic insert_user_agent Ar boolean
+.Pq Em optional
+Add meli User-Agent header in new drafts
+.\" default value
+.Pq Em true
 .It Ic default_header_values Ar hash table String[String]
 Default header values used when creating a new draft.
 .El

melib/src/email/compose.rs

@@ -60,10 +60,6 @@ impl Default for Draft {
             crate::datetime::timestamp_to_string(crate::datetime::now(), None),
         );
         headers.insert("Subject".into(), "".into());
-        headers.insert(
-            "User-Agent".into(),
-            format!("meli {}", option_env!("CARGO_PKG_VERSION").unwrap_or("0.0")),
-        );
         header_order.push("Date".into());
         header_order.push("From".into());
         header_order.push("To".into());

src/components/mail/compose.rs

@@ -171,6 +171,12 @@ impl Composer {
                 ret.draft.set_header(h, v.into());
             }
         }
+        if *mailbox_acc_settings!(context[account_hash].composing.insert_user_agent) {
+            ret.draft.set_header(
+                "User-Agent".into(),
+                format!("meli {}", option_env!("CARGO_PKG_VERSION").unwrap_or("0.0")),
+            );
+        }
         ret.pager
             .set_colors(crate::conf::value(context, "theme_default"));
         ret

src/conf/composing.rs

@@ -45,6 +45,10 @@ pub struct ComposingSettings {
     /// Default: true
     #[serde(default = "true_val", alias = "format-flowed")]
     pub format_flowed: bool,
+    ///Set User-Agent
+    ///Default: empty
+    #[serde(default = "true_val", alias = "insert_user_agent")]
+    pub insert_user_agent: bool,
     /// Set default header values for new drafts
     /// Default: empty
     #[serde(default, alias = "default-header-values")]
@@ -58,6 +62,7 @@ impl Default for ComposingSettings {
             editor_command: None,
             embed: false,
             format_flowed: true,
+            insert_user_agent: true,
             default_header_values: HashMap::default(),
         }
     }

src/conf/overrides.rs

@@ -221,6 +221,11 @@ pub struct ComposingSettingsOverride {
     #[serde(alias = "format-flowed")]
     #[serde(default)]
     pub format_flowed: Option<bool>,
+    #[doc = "Set User-Agent"]
+    #[doc = "Default: empty"]
+    #[serde(alias = "insert_user_agent")]
+    #[serde(default)]
+    pub insert_user_agent: Option<bool>,
     #[doc = " Set default header values for new drafts"]
     #[doc = " Default: empty"]
     #[serde(alias = "default-header-values")]
@@ -234,6 +239,7 @@ impl Default for ComposingSettingsOverride {
             editor_command: None,
             embed: None,
             format_flowed: None,
+            insert_user_agent: None,
             default_header_values: None,
         }
     }