Allow spider to specify custom callback

[seagatesoft]

Currently we can't specify callback for requests generated by HCF middleware. I am proposing new parameter on request.meta to allow the spider to specify the desired callback:

On the spider:
yield Request(url, meta={'use_hcf': True, 'hcf_params': {'qdata': {'callback': 'parse_item'}}})

This simple modification will implement that: seagatesoft@2adab90

I'll create the PR if this issue approved.

[BurnzZ]

Hi @seagatesoft,

I'm currently using this plugin on a project and this would feature would be super useful to us. Could we revive back this feature proposal? Thanks!