Add Mock services for Slurm and OPA to improve tests

app/api/dependencies.py

app/api/endpoints/workflow_execution.py

app/slurm/slurm_rest_client.py

app/tests/api/test_workflow.py

app/tests/api/test_workflow_execution.py

app/tests/conftest.py

app/tests/crud/test_workflow_version.py

app/tests/mocks/__init__.py

app/tests/mocks/authorization_service.py

app/tests/mocks/mock_opa_service.py

app/tests/mocks/mock_slurm_cluster.py

app/tests/mocks/slurm_cluster.py

app/tests/utils/utils.py

mako_templates/nextflow_command.template