Allow specifying extra cors headers for dapps (#4710)

parity/cli/mod.rs

@@ -181,6 +181,8 @@ usage! {
 			or |c: &Config| otry!(c.dapps).interface.clone(),
 		flag_dapps_hosts: String = "none",
 			or |c: &Config| otry!(c.dapps).hosts.as_ref().map(|vec| vec.join(",")),
+		flag_dapps_cors: Option<String> = None,
+			or |c: &Config| otry!(c.dapps).cors.clone().map(Some),
 		flag_dapps_path: String = "$BASE/dapps",
 			or |c: &Config| otry!(c.dapps).path.clone(),
 		flag_dapps_user: Option<String> = None,
@@ -428,6 +430,7 @@ struct Dapps {
 	port: Option<u16>,
 	interface: Option<String>,
 	hosts: Option<Vec<String>>,
+	cors: Option<String>,
 	path: Option<String>,
 	user: Option<String>,
 	pass: Option<String>,
@@ -674,6 +677,7 @@ mod tests {
 			flag_dapps_port: 8080u16,
 			flag_dapps_interface: "local".into(),
 			flag_dapps_hosts: "none".into(),
+			flag_dapps_cors: None,
 			flag_dapps_path: "$HOME/.parity/dapps".into(),
 			flag_dapps_user: Some("test_user".into()),
 			flag_dapps_pass: Some("test_pass".into()),
@@ -873,6 +877,7 @@ mod tests {
 				path: None,
 				interface: None,
 				hosts: None,
+				cors: None,
 				user: Some("username".into()),
 				pass: Some("password".into())
 			}),

parity/cli/usage.txt

@@ -164,6 +164,8 @@ API and Console Options:
                                  is additional security against some attack
                                  vectors. Special options: "all", "none",
                                  (default: {flag_dapps_hosts}).
+  --dapps-cors URL               Specify CORS headers for Dapps server APIs.
+                                 (default: {flag_dapps_cors:?})
   --dapps-user USERNAME          Specify username for Dapps server. It will be
                                  used in HTTP Basic Authentication Scheme.
                                  If --dapps-pass is not specified you will be