Marking fixtures as always-indirect

What's the problem this feature will solve?

I'm developing a pytest plugin that allows users to easily configure their fixtures: https://pypi.org/project/pytest-paramark/

One of the things I need for the plugin to be useful, is making all parametrizations of a given fixture indirect by default, so that users don't need to add parametrize(..., indirect=[...]) to all their tests.

I think such a feature would be also useful on its own.

Describe the solution you'd like

Add an optional parameter, so that one can write @pytest.fixture(indirect=True). This would:

• make all parametrizations of this fixture indirect
• disallow non-parametrized usage, unless the fixture provides defaults for all its arguments

Alternative Solutions

I've tried monkeypatching pytest inside the plugin to add this argument, but this is brittle, as I needed to dig deep into pytest's internals.
I'd rather have this included upstream, if possible.

Additional context

I'm happy to work on a PR if this is something you find interesting/useful.

No files, tests, or entry points are named. Start by locating pytest's fixture decorator and parametrization handling, then trace how indirect parameters are currently selected. Done means supporting @pytest.fixture(indirect=True) with the stated indirect behavior and non-parametrized usage restrictions, backed by tests.