BaseClient::GetPresignedPostFormData always returns unable to get presigned post form data; valid policy must be provided

[ijoseph]

Because !policy is always true here:

minio-cpp/src/baseclient.cc

Line 1070 in f5132e0

if (!policy) {

because the policy should be valid if it has an expiration, not if it lacks one -- this change is needed:

diff --git a/include/miniocpp/args.h b/include/miniocpp/args.h
index 2010b56..8132771 100644
--- a/include/miniocpp/args.h
+++ b/include/miniocpp/args.h
@@ -570,7 +570,7 @@ struct PostPolicy {
 
   ~PostPolicy() = default;
 
-  explicit operator bool() const { return !bucket.empty() && !expiration_; }
+  explicit operator bool() const { return !bucket.empty() && (bool) expiration_; }
 
   error::Error AddEqualsCondition(std::string element, std::string value);
   error::Error RemoveEqualsCondition(std::string element);

[balamurugana]

@ijoseph feel free to send a PR

[balamurugana]

fixed by #137