# Description

This PR adds an option to enable null-space control within
`OperationSpaceController` (following the discussions in #913).

## Details

Currently, `OperationSpaceController` controls only the task space,
which results in joint movements within the null-space of redundant
robotic manipulators. In general, it is desirable to have some control
over the robot null-space, e.g., to prevent the joints from going near
their limits. Hence, the PR adds the following:

- An optional nullspace (position) control integrated into
`OperationSpaceController`. This controller attracts the robot joints to
provided targets whereas possible, in parallel to the task-space target.
- Test cases for `OperationSpaceController` that use null-space control.
- Updates to the related tutorial script and documentation to use and
describe null-space control.
- Integration of (optional) null-space control to
`OperationSpaceControllerAction` with predefined joint targets, e.g.,
default joint positions, joint centers, zero joint position.
- Integration of null-space control to `"Isaac-Reach-Franka-OSC-v0"`
manager-based environment.

Null-space control utilizes either the dynamically consistent Jacobian
inverse or the Moore–Penrose inverse, depending on whether the full
inertia matrix is available.

## Type of change

- New feature (non-breaking change which adds functionality)
- This change requires a documentation update

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Signed-off-by: Özhan Özen <41010165+ozhanozen@users.noreply.github.com>
Co-authored-by: Kelly Guo <kellyguo123@hotmail.com>