Issue #245 - add additional input checks to `plot_correlations()`

[nikosbosse]

Description

This PR closes #245.

245 notes that you don't get a very informative error message if you pass something that's not the output of get_correlations() to plot_correlations().

This PR

• adds additional input checks to make sure that
  • the input is a data.frame
  • there is a metric column and all correlations are <= 1
• adds a test

I assume there would be potential to make all of this more sophisticated, but I think for now it should do the trick.

[Describe the changes that you made in this pull request.]

Checklist

• [x] My PR is based on a package issue and I have explicitly linked it.
• [x] I have included the target issue or issues in the PR title as follows: issue-number: PR title
• [x] I have tested my changes locally.
• [x] I have added or updated unit tests where necessary.
• [x] I have updated the documentation if required.
• [x] I have built the package locally and run rebuilt docs using roxygen2.
• [x] My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• [x] I have added a news item linked to this PR.
• [x] I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.34%. Comparing base (2ac7a6b) to head (da13115).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #729 +/- ## ========================================== + Coverage 95.32% 95.34% +0.01% ========================================== Files 21 21 Lines 1648 1655 +7 ========================================== + Hits 1571 1578 +7 Misses 77 77 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.