Add route to get workflow credentials as developer

.pre-commit-config.yaml

app/api/endpoints/workflow.py

app/api/endpoints/workflow_credentials.py

app/api/endpoints/workflow_execution.py

app/api/endpoints/workflow_version.py

app/crud/crud_workflow.py

app/git_repository/__init__.py

app/git_repository/github.py

app/schemas/workflow.py

app/schemas/workflow_execution.py

app/scm/scm.py

app/tests/api/test_workflow.py

app/tests/api/test_workflow_credentials.py

app/tests/api/test_workflow_execution.py

app/tests/conftest.py

app/tests/crud/test_workflow.py

app/tests/unit/test_scm.py