Request for testing of release candidate pyhf v0.7.0rc1

[pyhf announcements]

Dear pyhf users,

We'd like to solicit testing of release candidate pyhf v0.7.0rc1, which is out now on PyPI. v0.7.0rc1 is the first release candidate for minor release v0.7.0, and while there are two known regressions that need fixing before we can release v0.7.0, v0.7.0rc1 should be ready for API testing.

To install the release candidate you can either use pip install's --pre flag

```

python -m pip install --upgrade --pre pyhf

```

or specify the version number exactly

```

python -m pip install --upgrade 'pyhf==0.7.0rc1'

```

We welcome any feedback and questions that you have on GitHub Issues and Discussions. At least one more release candidate, v0.7.0rc2, is planned before v0.7.0 is released so there will be a short period of time to incorporate feedback before the final release. As a reminder, v0.7.0 will not contain all requested features made since the last release, and we instead plan to increase the future release cadence with smaller releases to better roll out new features and fixes faster.

Thank you for your patience. Please don't hesitate to contact us through the recommended channels!

Best,
The pyhf dev team (Lukas, Matthew, and Giordon)