code: func (g *Gitlab) AddProjectDeployKey(id, title, key string) (*ResponseMeta, error) {
  	u := g.ResourceUrl(ProjectDeployKeysApiPath, map[string]string{":id": id})
  
  	var err error
  
  	v := url.Values{}
  	v.Set("title", title)
  	v.Set("key", key)
  
  	body := v.Encode()
  
  	_, meta, err := g.buildAndExecRequest("POST", u.String(), []byte(body))
  
  	return meta, err
  }
docs: /*
  Add deploy key to project.
  
      POST /projects/:id/keys
  
  Parameters:
  
      id    The ID of a project
      title The key title
      key   The key value
  
  */