Implement easier adding of multi-value http headers

[DazKins]

There are currently 2 SetHeaders functions with the following types:

func(headers map[string]string) *resty.Request
func(header string, value string) *resty.Request

It might be convenient to add a 3rd:

func(headers map[string][]string) *resty.Request

As listed in RFC2616 HTTP headers can have multiple values: https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

This would also be convenient as the inbuilt golang http.Header type is defined as map[string][]string so would allow for direct usage of that type:

headers := http.Header{}
restyClient.R().SetHeaders(headers)

[mhdiiilham]

Hey @DazKins is anyone already working on this? If not, I'd be glad if you assign this to me

[DazKins]

Hey @DazKins is anyone already working on this? If not, I'd be glad if you assign this to me

Hey, I don't have permission to assign, but no I don't believe anyone is working on this

[mhdiiilham]

Hey @DazKins is anyone already working on this? If not, I'd be glad if you assign this to me

Hey, I don't have permission to assign, but no I don't believe anyone is working on this

Hey @moorereason, could you assign this to me?