I have tried with both soapui OS 5.5.0 and 5.6.0 that when (in REST/POST with multipart/formdata and post queryString checked) I attach a .csv file to attachment tab by default gets content type : application/octate-stream and my api service throwing error invalid content type "application/octate-stream" , upload a file with content type "text/csv" . Even I change it to text/csv then also in raw i can see soap ui itself sending it as "application/octate-stream" . So i am unable to test this scenario of sending multipart form data with csv attachment.
Note: The scenario is working correctly with my Ready Api 3.3.0 licensed version as it is considering the csv file as text.csv.
Also in post man able to hit the api for same csv file
So request to update me or the OS version of soapui to consider .csv file as "text/csv" instead of "application/octate-stream"
After discussing the issue with my dev team that the CSV file is getting "application/octate-stream" in soap ui, he has changed the code so that now the REST call with CSV attachment and "application/octate-stream" as its content type getting processed by the webService. I can say it is the design for the files like word, excel or any exe kind the soap ui is designed to have "application/octate-stream" as content type.
So now "application/octate-stream" input of csv file is accepted by webservice and issue is resolved.