add operator to experiment terminations

[aabills]

Description

Adds operator for experiment terminations. While this won't functionally change many experiments, it enables experiments to more closely mirror cell testing protocols.

Fixes # (issue)

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ pre-commit run (or $ nox -s pre-commit) (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
• All tests pass: $ python -m pytest (or $ nox -s tests)
• The documentation builds: $ python -m pytest --doctest-plus src (or $ nox -s doctests)

You can run integration tests, unit tests, and doctests together at once, using $ nox -s quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.69%. Comparing base (ef8571c) to head (5f40794).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4770   +/-   ##
========================================
  Coverage    98.69%   98.69%           
========================================
  Files          303      303           
  Lines        23226    23256   +30     
========================================
+ Hits         22923    22953   +30     
  Misses         303      303           

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

[valentinsulzer]

Good idea including this, do most cyclers ask for a direction or do they figure it out automatically?

[aabills]

Good idea including this, do most cyclers ask for a direction or do they figure it out automatically?

Neware and Maccor, the only ones I've dealt with, have "charge" or "discharge" built into the steps and they also have these limits specified with operators.

The reason for this is so that they can go to a "safer" state in case of a short or something. This of course is not relevant for pybamm, but there's not a great way to filter the safety limits without catching the other limits.

[aabills]

this idaklu error doesn't look related to this pr

[kratman]

this idaklu error doesn't look related to this pr

Yeah it is a flaky test, not sure why that happens, but I have not really been able to reproduce it locally. Re-triggering it should make it pass. It is on my to-do list