Angular 8 can't upload formdata/multi-part to server - http-post

Question

I'm trying to upload a xlsx file to server, but I receive two different errors, whether I specify the contentType in the http request header or not. If I specify "Content-type: multipart/form-data" I get the following error:
FileUploadException: the request was rejected because no multipart
boundary was found
Then, if I do not specify the content type (as proposed in different answers), I get this error:
current request is not a multipart request
This is what I do to upload the file. HTML (input fired by a button that calls an uploadFile() method):
<input type="file" #fileUpload id="fileUpload" name="fileUpload" accept=".xlsx" style="display:none;" />
.ts:
uploadFile() {
const fileUpload = this.fileUpload.nativeElement;
fileUpload.onchange = () => {
this.file = fileUpload.files[0];
this.uploadFileToServer();
};
fileUpload.click();
}
uploadFileToServer() {
const formData = new FormData();
formData.append('file', this.file);
this.importService.uploadFile(formData).subscribe(d => {
});
}
In the service the method does this:
this.http.post(
apiUrl,
formData,
options
);
where in options there are the specified headers:
let applicationHeaders = new HttpHeaders();
applicationHeaders = applicationHeaders.append('Content-type', 'multipart/form-data');
multipart or blank.
In the POST request in the request payload I have:
------WebKitFormBoundarytNckytdr7I8wQcuc
Content-Disposition: form-data; name="file"; filename="Template (2).xlsx"
Content-Type: application/octet-stream
------WebKitFormBoundarytNckytdr7I8wQcuc--