The API Gateway is sending an undesired content-type in the Route via HTTP(S) assertion to the backend, causing the request sent to the backend to fail. The backend is expecting a content-type of application/json (for example) and the Gateway is sending text/xml. This article will discuss how to set the desired content-type.
The Gateway will - by default - use the content-type specified in the request, which may not always be desirable by the backend.
This affects all supported Gateway versions.
Various headers can be overwritten by using the Manage Transport Properties/Headers assertion.
The headers can be manipulated in the Route via HTTP(S) assertion too by following the instructions in the documentation here which walks through three different use-cases: https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/layer7-api-management/api-gateway/9-4/policy-assertions/assertion-palette/message-routing-assertions/route-via-http-s-assertion.html#concept.dita_049ffc6cf73f4e1b368ebb8707b00fe50b5546cc_manipulating