fix OAuth client credentials content type override (#957)

- Bugfix: OAuth client credentials token request now sends correct `application/x-www-form-urlencoded` content type
- Improvement: HTTP client Content-Type in additional headers now overrides the payload content type

1 files changed, 11 insertions, 0 deletions

diff --git a/src/zenhttp/httpclient_test.cpp b/src/zenhttp/httpclient_test.cpp
index 67cbaea9b..deaeca2a8 100644
--- a/src/zenhttp/httpclient_test.cpp
+++ b/src/zenhttp/httpclient_test.cpp
@@ -414,6 +414,17 @@ TEST_CASE("httpclient.post")
 		CHECK_EQ(Resp.AsText(), "{\"key\":\"value\"}");
 	}
 
+	SUBCASE("POST with content type override via additional header")
+	{
+		const char* Payload = "test payload";
+		IoBuffer	Buf(IoBuffer::Clone, Payload, strlen(Payload));
+
+		HttpClient::Response Resp = Client.Post("/api/test/echo", Buf, ZenContentType::kJSON, {{"Content-Type", "text/plain"}});
+		CHECK(Resp.IsSuccess());
+		CHECK_EQ(Resp.AsText(), "test payload");
+		CHECK_EQ(Resp.ResponsePayload.GetContentType(), ZenContentType::kText);
+	}
+
 	SUBCASE("POST with CbObject payload round-trip")
 	{
 		CbObjectWriter Writer;