Make bearer token optional

AppleLibs/Network/Requests/Request.swift

@@ -36,9 +36,9 @@ public struct BasicAuthentication: Authentication
 
 public struct BearerToken: Authentication
 {
-    private let token: String
+    private let token: String?
     
-    public init(token: String) {
+    public init(token: String?) {
         self.token = token
     }
 
@@ -46,6 +46,9 @@ public struct BearerToken: Authentication
         "Authorization"
     }
     public var headerValue: String? {
+        guard let token = token else {
+            return nil
+        }
         return "Bearer \(token)"
     }
 }