Add an operator| (pipe) for future folding and channels

include/continuable/continuable-base.hpp

@@ -323,6 +323,19 @@ public:
     return std::move(*this).fail([](auto&&) {});
   }*/
 
+  /// The pipe operator | is an alias for the continuable::then method.
+  ///
+  /// \param right The argument on the right-hand side to connect.
+  ///
+  /// \returns See the corresponding continuable::then method for the
+  ///          explanation of the return type.
+  ///
+  /// \since version 2.0.0
+  template <typename T>
+  auto operator|(T&& right) && {
+    return std::move(*this).then(std::forward<T>(right));
+  }
+
   /// Invokes both continuable_base objects parallel and calls the
   /// callback with the result of both continuable_base objects.
   ///

test/playground/test-playground.cpp

@@ -69,17 +69,12 @@ struct my_callable {
 int main(int, char**) {
   http_request("github.com").flow(my_callable{});
 
-  http_request("github.com")
+  http_request("github.com") | [](std::string) {
-      .then([](std::string) {
     // ...
     return 0;
-      })
+  } | [] {
-      .fail([](std::error_condition) {
     // ...
-      })
+  };
-      .then([] {
-        // ...
-      });
 
   http_request2("github.com")
       .then([](std::string) {