fix: unpublish preview for Multi-language

[Duaner]

Problem
When building the preview page for a specific Custom type, a lang is set statically in the context and not properly replaced by the one passed through the URL Path or QueryString.

Fixes #86

Description

We now use only queryString for unpublished documents since we had conflict in the router. In development, if you were using the DefaultLang option and tried to preview an unpublish doc, the 404 was always showing. We bypassed that by using queryString for all unpublished docs. If the doc is already published we redirect to a pretty URL.

Added a new utils to get QueryString as JSON

Bug fixes

• fix previews in multi-lang project

Breaking changes

• path is no longer used in gatsby-config.js; you should use match to define your pages path ; and you can use previewPath if you want to change the default route for unpublished document preview page

I also updated to the newest toolbar that should Fix #126

[MadsMadsDk]

Looking forward to this one getting merged.

[Duaner]

I just realized that there is still a problem there. When you use default lang, the URL for the preview page is properly set but doesn't load properly the preview component but the 404 page.

I will see what i can do for this next week.

[MadsMadsDk]

@Duaner Did you make any progress on this? :)

[jdwillemse]

@veloce a Prettier check fails on your last commit

[ruslansavenok]

For anyone who needs a fix before this gets merged, just hardcode urls for each langauge in pages: [] instead of using :lang?:

{
  type: 'Blog_post',
  match: '/it/blog/:uid',
  path: '/it/blog-preview',
  component: require.resolve('./src/templates/blog_post.js'),
  langs: ['it-it'],
},
{
  type: 'Blog_post',
  match: '/blog/:uid',
  path: '/blog-preview',
  component: require.resolve('./src/templates/blog_post.js'),
  langs: ['en-us'],
},