Update PasswordStorage.keychain implementation

Sources/XXMessengerClient/Utils/PasswordStorage+Keychain.swift

@@ -3,18 +3,20 @@ import XXClient
 
 extension PasswordStorage {
   public static let keychain: PasswordStorage = {
-    let keychain = KeychainAccess.Keychain(
-      service: "xx.network.client.messenger"
-    )
+    let keychain = KeychainAccess.Keychain(service: "xx.network.client.messenger")
+    let key = "password"
     return PasswordStorage(
       save: { password in
-        keychain[data: "password"] = password
+        keychain[data: key] = password
       },
       load: {
-        guard let password = keychain[data: "password"] else {
+        guard let password = keychain[data: key] else {
           throw MissingPasswordError()
         }
         return password
+      },
+      remove: {
+        try keychain.remove(key)
       }
     )
   }()