Return 400 instead of 500 from upload OTLP endpoint #6598
Description
Related to this UI issue jaegertracing/jaeger-ui#2589
The UI asks the server to transform (http://localhost:16686/api/transform) data in OTLP into Jaeger UI model. If the payload is malformed the server responds with a 500 status code, which is incorrect since this is a user error and the status code should be one of 400s.
{"data":null,"total":0,"limit":0,"offset":0,"errors":[{"code":500,"msg":"cannot unmarshal OTLP : readUint32: unexpected character: \ufffd, error found in #10 byte of ...|esCount\":-1}],\"links|..., bigger context ...|AR to the classpath\"}}],\"droppedAttributesCount\":-1}],\"links\":[],\"status\":{\"code\":2},\"flags\":257},{\"|..."}]}