retrofit2 with 2 multiparts - JSON and File is failed - retrofit2

Question

I'm trying to call an external ReST service.
retrofit_version = "2.9.0"
okhttp = "3.14.9"
This is the Retrofit interface as I define it:
#Multipart
#POST("orgs/{orgUuid}/patients/{patientId}/documents")
Call<DocUploadRes> uploadDocForPatient(#Header("Authorization") String authorization,
#Path("orgUuid") String orgUuid,
#Path("patientId") Integer patientId,
#Part("metadata") RequestBody metadata,
#Part MultipartBody.Part file);
My Client call is as follow:
RequestBody metadataBody = RequestBody.create(MediaType.parse("application/json"), content);
MultipartBody.Part filePart = MultipartBody.Part.createFormData("file","Safereport", RequestBody.create(MediaType.parse("application/pdf"), file.getBytes()));
Response<DocUploadRes> response = pccPatientRestApi.uploadDocForPatient(getBearerAuthHeader(pccAccessToken), pccOrgUuid, patientId, jsonPart, filePart).execute();
When I'm running this code with retrofit I'm getting Bad Request from the server with:
status":"400","title":"Bad Request.","detail":"File type is not supported"
But when I run the same service from postman it working successfully with the following http request sent:
POST /api/public/preview1/orgs/E58A8604-38F2-4098-879E-C6BCC6D01EB8/patients/372842/documents HTTP/1.1
Host: connect2.pointclickcare.com
Authorization: Bearer iy8OUOVa46oxaYRMVYlRApqDW00m:2Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
----WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="file"; filename="/C:/Users/user/Desktop/RosieConnect-20-API-User-Manual-Ver-07172018.pdf"
Content-Type: application/pdf
(data)
----WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="metadata"
{"documentCategory":1,"documentName":"Safebeing Report","effectiveDate":"2020-05-26T08:03:49.895Z"}
----WebKitFormBoundary7MA4YWxkTrZu0gW
It seems to me that retrofit doesn't send the 'application/pdf' in the Content-Type header of the file #Part... how can it be fixed?
Any idea will be very much appreciated!
-- Update ---
It appears the the file extension is mandatory.
Problem solved by adding .pdf to the file name
MultipartBody.Part filePart = MultipartBody.Part.createFormData("file","report.pdf", RequestBody.create(MediaType.parse("application/pdf"), file.getBytes()));