To inject new headers into a request using the GUI, you must make the edits in the Endpoint Designer section of your API Definition:
Step 1: Add an Endpoints and select the Modify Headers option
You must also set a method and a request pattern to match against. These patterns can contain wildcards in the form of any string bracketed by curly braces. These wildcards are so they are human readable and do not translate to variable names. Under the hood, a wildcard translates to the “match everything” regex of:
Step 2: Select the “Request” tab, this ensures that this will only be applied to inbound requests
Step 3: Select set the headers to Delete and the headers to insert using the provided fields, remember to press the “+” button to ensure they are added to the list.
Step 4: Save the API
Once the API is saved, if a request path and method matches your pattern, then the relevant modifications will be made to the request that hits your endpoint.