DX: Unify Docker mount points and paths (#7549)

CONTRIBUTING.md

@@ -67,7 +67,7 @@ Sometimes it can be more convenient to have a shell inside the container:
 
 ```console
 docker compose run php-7.4 sh
-/app vendor/bin/phpunit
+/fixer vendor/bin/phpunit
 ```
 
 The images come with an [`xdebug` script](github.com/julienfalque/xdebug/) that allows running any PHP command with Xdebug enabled to help debug problems.

compose.yaml

@@ -8,9 +8,9 @@ services:
         ALPINE_VERSION: "3.16"
         PHP_VERSION: "7.4"
         PHP_XDEBUG_VERSION: "3.1.6"
-    working_dir: /app
+    working_dir: /fixer
     volumes:
-      - .:/app
+      - .:/fixer
     environment:
       PHP_IDE_CONFIG: serverName=php-cs-fixer
       PHP_CS_FIXER_ALLOW_XDEBUG: 1
@@ -47,9 +47,9 @@ services:
   sphinx-lint:
     build:
       target: sphinx-lint
-    working_dir: /app
+    working_dir: /fixer
     volumes:
-      - .:/app
+      - .:/fixer
 
   markdown-lint:
     image: registry.gitlab.com/pipeline-components/markdownlint:latest

docker/xdebug.ini

@@ -9,5 +9,5 @@ xdebug.discover_client_host = true
 xdebug.client_host = host.docker.internal
 
 ; Required so XDebug DOES NOT print warning "Could not connect to debugging client"
-xdebug.log = /app/docker/php/xdebug.log
+xdebug.log = /fixer/docker/php/xdebug.log
 xdebug.log_level = 1