add 'method' to namedtuple Field to support field filtering on Link method

[vdejager]

add 'method' to namedtuple Field to support field filtering on Link method in DRF AutoSchema manual fields

[lovelydinosaur]

I don't really understand the change as proposed.

[vdejager]

The idea here was to support field description on a specific endpoint's method. i.e. a GET request to a certain endpoint may have a particular query parameter and the POST request to the same endpoint might accept a body parameter. It should be able to annotate them differently. The current way of endpoint annotation adds the parameter description to all allowed request types.

[lovelydinosaur]

Use different sets of fields on each link for that case.