code: function setSkin ({accessToken}, profileId, skinUrl, isSlim = false) {
    const params = new URLSearchParams()
    params.append('model', isSlim ? 'slim' : '')
    params.append('url', skinUrl)
  
    return fetch(`${CORE_API}/user/profile/${profileId}/skin`, {
      method: 'POST',
      body: params,
      headers: {
        'user-agent': USER_AGENT,
        'authorization': `Bearer ${accessToken}`
      }
    })
      .then(handleErrors)
      .then(res => null)
  }
docs: Sets a logged-in user's in-game skin to an online image.
  
  @param {Object} session - object from authentication
  @param {string} session.accessToken - valid access token for the user's account
  @param {string} profileId - which profile UUID to update the skin of
  @param {string} skinUrl - Internet-accessible URL of the image file
  @param {boolean} [isSlim] - if true, the slim model will be used with the skin
  @returns {Promise} resolves if access token, profile UUID, and skin URL are valid
  @see {@link http://wiki.vg/Mojang_API#Change_Skin}