Make it possibility to overwrite the prefix *api* and do not ignore the site base path

[vzz3]

Issue

Problem 1

Routing slugs are treated as absolute paths and not relative to the site configuration URL.
Consider the following example
* base URL in the TYPO3 site config: http://localhost:7080/rest
* path of a route in ext/Configuration/Routes.yml: api/v1/login

Requesting just http://localhost:7080/api/v1/login will not work since TYPO3 would not be able to find the site configuration (TYPO3\CMS\Frontend\Middleware\SiteResolver).
On the other hand requesting http://localhost:7080/rest/api/v1/login will lead to the problem that LMS\Routes\Extbase\RouteHandler will not be able to match the route, since it tries to match the entire requested path (rest/api/v1/login) and not only the path below the site base path (rest), which would only be (api/v1/login).

Problem 2

The prefix api of the route path is hardcoded in LMS\Routes\Routing\RestApiEnhancer. Therefore, all routes in any Routes.yml that does not start with api/ will never work.

Improvements in this Patch

This patch adds the possibility to overwrite the prefix api of the route path in LMS\Routes\Routing\RestApiEnhancer with the routeEnhancers configuration pathPrefix. This, makes it possible to configure routes in a Routes.yml, that do not need to beginn with api/.
Furthermore, the site base path is taken into account wen matching routes in the LMS\Routes\Extbase\RouteHandler. This makes it possible to use this extension on sites that does not have an empty site base path in the TYPO3 site config (e.g. http://localhost:7080/rest)

Possible sample configuration:

• Endpoint: http://localhost:7080/rest/pos/api/v1/login
• TYPO3 site config example:

  base: 'http://localhost:7080/rest'
  routeEnhancers:
      ApplyRoutesCollection:
          type: Routes
          # added functionality:
          pathPrefix: 'pos/api'
  

• Routes.yml example:

   api_access-login:
       # path does not need to start with api anymore
       path: pos/api/v1/login
       controller: VENDOR\myext\Controller\AccessController::login
       methods: [POST]
       format: json
       defaults:
           vendor: VENDOR
           extension: myext
           plugin: Api
  

[cepheiVV]

The base URL problem also occurs with a language setup that uses prefixes in the URL like base: /en/:

languages:
  -
    title: English
    enabled: true
    base: /en/
    typo3Language: default
    locale: en_GB.UTF-8
    iso-639-1: en
    websiteTitle: medbase
    navigationTitle: EN
    hreflang: en-GB
    flag: gb
    direction: ltr
    languageId: 0

This PR doesn't solve the base URL prefix problem for language setups.