Enable scoped references in `mkdocs`

[llucax]

What's needed?

In mkdocstrings-python 1.19, finally we can write relative and scoped references in docs, avoiding the huge strings to do cross references:

class VeryLongClassName:

    some_prop: int
    """Some doc.

    This does whatever with [some_meth()][frequenz.some.package.very.nested.and.with.VeryLongClassName.some_meth].
    """

    def some_meth(): ...

Now can be something like:

[`some_meth()`][some_meth]

Proposed solution

Depend on 1.19 and enable the new options in the templates and this project:

plugins:
- mkdocstrings:
    handlers:
      python:
        options:
          relative_crossrefs: true
          scoped_crossrefs: true

Use cases

No response

Alternatives and workarounds

No response

Additional context

Limitations of scoped cross-refs:

Cross-referencing an imported object will directly link to this object if the objects inventory of the project it comes from was loaded. You won't be able to cross-reference it within your own documentation with scoped references, if you happen to be rendering this external object too. In that case, you can use an absolute reference or a relative one instead.

Another limitation is that you won't be able to reference an external package if its name can be resolved in the current object's scope.