[server] schema/doc/serializers: FileField type is always string/binary

[gnuletik]

For example, the retrieveItem operation's return type (you need to click on the 200 button to show the response types) is described as string <binary>.
In fact, the input type is string <binary> but the return type should be string <url>.

The OpenAPI specs example has an example for file uploads but there is no example on how it should behave with a Component referenced (as the schema is using).

Maybe we should use a different component for the request type and response type?

[Tointoin]

You're PR doesn't seems to provoke the problem:
I have got same beahaviour in schema generation with FileField with regular DRF 3.11 i. e. source_file gives string <binary> type with request and response

[gnuletik]

Ok, good to know :) Thanks for having a look at it @Tointoin !
It seems that there is an open issue about it on DRF repo : encode/django-rest-framework#6863