test: use tox-poetry plugin for tox

tox.ini

@@ -1,13 +1,10 @@
 [tox]
-isolated_build = true
+requires =
+    tox-poetry
+    poetry
 envlist = check, apply-check, docs, tests, build
 
 [testenv]
-install_command = pip install {opts} {packages}
-deps =
-    poetry>=1.1.13
-commands_pre =
-    bash -c "python -m pip install -r <(poetry export --dev --extras=docs --without-hashes --no-interaction)"
 whitelist_externals =
     bash
 
@@ -24,16 +21,19 @@ commands =
     isort src/keycloak tests docs
 
 [testenv:docs]
+extras = docs
 commands =
     sphinx-build -T -E -W -b html -d _build/doctrees -D language=en ./docs/source _build/html
 
 [testenv:tests]
 setenv = file|tox.env
+passenv = CONTAINER_HOST
 commands =
     ./test_keycloak_init.sh "pytest -vv --cov=keycloak --cov-report term-missing {posargs}"
 
 [testenv:build]
-commands_pre =
+deps = 
+    poetry
 setenv =
     POETRY_VIRTUALENVS_CREATE = false
 commands =