Add coverage job

Insert python coverage job for py-test

Co-Authored-By: Nguyen Hai Truong <truongnh@vn.fujitsu.com>
Change-Id: Ia10a45cfc01f9ec2757c7117f9d8d252a90e07bd

.zuul.yaml

@@ -2,6 +2,7 @@
     queue: freezer
     templates:
       - check-requirements
+      - openstack-cover-jobs
       - openstack-python3-jobs
       - openstack-python3-jobs-arm64
       - publish-openstack-docs-pti

tox.ini

@@ -44,6 +44,18 @@ basepython = python3.9
 [testenv:py312]
 basepython = python3.12
 
+[testenv:cover]
+basepython = python3
+setenv =
+    {[testenv]setenv}
+    PYTHON=coverage run --source freezerclient --parallel-mode
+commands =
+    stestr run {posargs}
+    coverage combine
+    coverage html -d cover
+    coverage xml -o cover/coverage.xml
+    coverage report
+
 [testenv:docs]
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -b html doc/source doc/build/html