Support extending model with anonymous field

[davidfou]

Hi,

First, I'm a beginner with Golang. Maybe I didn't respect best practices, you should double check my PR.

The idea is to support fields added my composing a struct with an anonymous field. Here is an example with encoding/json package.

Instead of making it implicit, a new tag attribute extend is added to declare an anonymous field as an extension of the current struct

type Base struct {
	CreatedAt time.Time `jsonapi:"attr,created_at"`
	UpdatedAt time.Time `jsonapi:"updated_at"`
}

type Blog struct {
	Base      `jsonapi:"extend"`
	ID        int       `jsonapi:"primary,blogs"`
	Title     string    `jsonapi:"attr,title"`
	ViewCount int       `jsonapi:"attr,view_count"`

}

Also, the code about model reflection was duplicated in request.go and response.go. It's now factorized in helper.go and it's used constants (no more like this one).

[davidfou]

Someone here?

[svperfecta]

hey @DFournier looks like you're addressing #21 right?

[svperfecta]

Also, how do you like this vs. #78

[davidfou]

@genexp sure, this PR is related to #21. The only difference is the new the tag extend which makes it explicit.

#78 looks like to address the same issue except it breaks the API.

[svperfecta]

I like your approach best myself as well. I'd like to see metadata make the relationship explicit too.

…

On Sat, May 13, 2017 at 8:21 AM David Fournier ***@***.***> wrote: @genexp <https://github.com/genexp> sure, this PR is related to #21 <#21>. The only difference is the new the tag extend which makes it explicit. #78 <#78> looks like to address the same issue except it breaks the API. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#87 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAADMJQfI6LrfTYEyQqmsOksIFLV5gO9ks5r5aBBgaJpZM4NNSiG> .

[davidfou]

Also, I don't think the field must be anonymous in order to support the extend tag.

About meta, why not! Maybe the lib should handle both in order to not introduce a breaking change but log a depreciation warning about the usage of Meta interface? I don't know the golang library best practices.