Epic : missing options for creation/update

[nicolasbrechet]

Hi,

In the CreateEpicOptions struct, we're missing some options, which in my case prevents me from creating a "child" Epic

go-gitlab/epics.go

Line 176 in 1fb53be

type CreateEpicOptions struct {

• color
• confidential
• created_at
• parent_id

And as well in UpdateEpicOptions

go-gitlab/epics.go

Line 213 in 1fb53be

type UpdateEpicOptions struct {

• add_labels
• parent_id
• remove_labels
• updated_at
• color

I'm working on a PR to fix this