ERROR: Directive 'jinja' cannot be mocked: MockingError: MockStateMachine has not yet implemented attribute 'insert_input'

[ice-tong]

Hi, thanks for the nice work! I found sphinx-jinja2 very useful when I needed to customise the generated documentation.

Since the generated documentation contains markdown syntax, I try to use myst-parser with sphinx-jinja2, but encountered the following error:

I’d be really grateful if you had any suggestions that could help me with this issue!

[eudoxos]

The template output is fed back into the RST parser. When the source uses MyST parser (please confirm), this error will be triggered:

   Directive 'jinja' cannot be mocked: MockingError: MockStateMachine has not yet implemented 'insert_input'.

The workaround is to wrap the jinja directive inside rst-eval

```{rst-eval}
   .. jinja::
      :ctx: {"foo":"bar"}

      Baz.
```

rather than using it directly:

```{jinja}
   :ctx: {"foo":"bar"}

   Baz.
```

[LecrisUT]

The issue might be not too hard to fix. It might be just switching to state.nested_parse in

sphinx-jinja2/src/sphinx_jinja2/__init__.py

Line 195 in 4731a17

self.state_machine.insert_input(new_lines, source)