Mock multipart response without relation id from arrow part name

[NRHelmi]

More context in this jira ticket https://relationalai.atlassian.net/browse/RAI-12507

[denisgursky]

Hm, I thought that we were going to send 0.arrow as the name.

https://www.ietf.org/rfc/rfc2388.txt
says

Each field has a name. Within a given form, the names are unique.

So we can't have empty names, if I'm reading the spec right.

Also, I suspect that the multipart parser might just throw an error if there're multiple parts with empty names.

UPD:

Chrome's parser seems to be handling it fine.

UPD2:

Well, kinda fine

----------------------------656399404245038028349435
Content-Disposition: form-data; name=""

my value1
----------------------------656399404245038028349435
Content-Disposition: form-data; name="abc"

my value2
----------------------------656399404245038028349435
Content-Disposition: form-data; name=""

my value3
----------------------------656399404245038028349435--

It just ignores the 3rd part when form.get("").