Connector default headers overwrite request body headers

[Sammyjo20]

I recently ran into an issue where my connector had a default Content-Type of application/json and the request had a different Content-Type added by the body trait (HasFormBody) but because of the new PendingRequest order, the connector headers were overwriting the trait's headers.

I think in future versions of Saloon it should work like so:

• Trait Headers for connector
• Default Headers for connector THEN
• Merge trait headers from request
• Merge default headers from request