Make error message for unknown boundary name more helpful

[efaulhaber]

main:

ERROR: Key :bottom is not a valid boundary name

This PR:

ERROR: Key :bottom is not a valid boundary name. Valid names are [:Left, :Bottom, :Right, :Top].

[github-actions]

Review checklist

This checklist is meant to assist creators of PRs (to let them know what reviewers will typically look for) and reviewers (to guide them in a structured review process). Items do not need to be checked explicitly for a PR to be eligible for merging.

Purpose and scope

• The PR has a single goal that is clear from the PR title and/or description.
• All code changes represent a single set of modifications that logically belong together.
• No more than 500 lines of code are changed or there is no obvious way to split the PR into multiple PRs.

Code quality

• The code can be understood easily.
• Newly introduced names for variables etc. are self-descriptive and consistent with existing naming conventions.
• There are no redundancies that can be removed by simple modularization/refactoring.
• There are no leftover debug statements or commented code sections.
• The code adheres to our conventions and style guide, and to the Julia guidelines.

Documentation

• New functions and types are documented with a docstring or top-level comment.
• Relevant publications are referenced in docstrings (see example for formatting).
• Inline comments are used to document longer or unusual code sections.
• Comments describe intent ("why?") and not just functionality ("what?").
• If the PR introduces a significant change or new feature, it is documented in NEWS.md.

Testing

• The PR passes all tests.
• New or modified lines of code are covered by tests.
• New or modified tests run in less then 10 seconds.

Performance

• There are no type instabilities or memory allocations in performance-critical parts.
• If the PR intent is to improve performance, before/after time measurements are posted in the PR.

Verification

• The correctness of the code was verified using appropriate tests.
• If new equations/methods are added, a convergence test has been run and the results
  are posted in the PR.

Created with ❤️ by the Trixi.jl community.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (45e7dc2) 96.24% compared to head (157afec) 96.24%.

Files	Patch %	Lines
...ers/dgsem_unstructured/sort_boundary_conditions.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1762   +/-   ##
=======================================
  Coverage   96.24%   96.24%           
=======================================
  Files         431      431           
  Lines       34895    34895           
=======================================
  Hits        33582    33582           
  Misses       1313     1313           

Flag	Coverage Δ
unittests	96.24% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ranocha]

Thanks!

[bennibolm]

LGTM

[efaulhaber]

Failing tests seem to be unrelated to my changes.

[ranocha]

It looks unrelated to this PR - and it also happens in other CI runs, e.g., the formatter PR #1759. We should try to understand what's going on.