fix: url_prefix behaviour

[juanpicado]

• Update reverse proxy docker examples for v4 ( just moved examples docs: copy docker examples v4 #2120 )
• Update them UI (this version of the UI does not contain assets anymore, svg, png, fonts or css, only JS).
• Document better the url_prefix feature
• Update documentation website
• Add base html and better config feat: api provider and config provider ui#608
• Add environment variable to override headers https behnid reverse proxy without headers #2129
• Custom favicon Use custom favicon  #1593
• Improve host header validation

This fix is based on #2070 for the next major, but I plan to move some fix to the v4 so we can solve this situation with no breaking changes.

Scheduled release: next minor

url_prefix

The new internal logic builds correctly the public url, validates the host header and and bad shaped url_prefix.

eg: url_prefix: /verdaccio, url_prefix: verdaccio/, url_prefix: verdaccio would be /verdaccio/

Public URL

The new VERDACCIO_PUBLIC_URL is intended to be used behind proxies, this variable will be used for:

• Used as base path to serve UI resources as (js, favicon, etc)
• Used on return metadata dist base path
• Ignores host and X-Forwarded-Proto headers
• If url_prefix is defined would be appened to the env variable.

VERDACCIO_PUBLIC_URL='https://somedomain.org';
url_prefix: '/my_prefix'

// url -> https://somedomain.org/my_prefix/

VERDACCIO_PUBLIC_URL='https://somedomain.org';
url_prefix: '/'

// url -> https://somedomain.org/

VERDACCIO_PUBLIC_URL='https://somedomain.org/first_prefix';
url_prefix: '/second_prefix'

// url -> https://somedomain.org/second_prefix/'

Custom favicon

The favicon can be replaced in 2 ways:

Local absolute path

web:
  title: Verdaccio
  logo: /home/user/favicon.ico

By URL

web:
  title: Verdaccio
  logo: https://somedomain.org/favicon.ico

If the logo is not defined, will fetch (and bundled in) the custom verdaccio favicon

UI

• Does not contain any CSS, SVG or Fonts anymore
• Only JS
• Ability add your own CSS, JS at the HTML

Web new properties for dynamic template

The new set of properties are made in order allow inject html and JavaScript scripts within the template. This
might be useful for scenarios like Google Analytics scripts or custom html in any part of the body.

• metaScripts: html injected before close the head element.
• scriptsBodyAfter: html injected before close the body element.
• bodyAfter: html injected after verdaccio JS scripts.

web:
  scriptsBodyAfter:
    - '<script type="text/javascript" src="https://my.company.com/customJS.min.js"></script>'
  metaScripts:
    - '<script type="text/javascript" src="https://code.jquery.com/jquery-3.5.1.slim.min.js"></script>'
    - '<script type="text/javascript" src="https://browser.sentry-cdn.com/5.15.5/bundle.min.js"></script>'
    - '<meta name="robots" content="noindex" />'
  scriptsbodyBefore:
    - '<div id="myId">html before webpack scripts</div>'