Fix naming of some activity/capacity-related things

[alexdewar]

Description

I've a renamed a couple of activity-related things for consistency/clarity:

1. I renamed the cap2act field and CSV column to capacity_to_activity. We've previously expanded out these kinds of abbreviations elsewhere and I think it makes things more readable. (I suppose we could name it something else, like activity_per_capacity instead)
2. For the map which we use to work out capacity/availability constraints, I think we should be talking about "activity limits" rather than "capacity limits". I've renamed some data structures and fields to reflect this. This makes sense to me, but please let me know if you think I'm not using the term activity correctly.

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc

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 95.11%. Comparing base (55d7c49) to head (740ae51).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #441   +/-   ##
=======================================
  Coverage   95.11%   95.11%           
=======================================
  Files          32       32           
  Lines        4751     4752    +1     
  Branches     4751     4752    +1     
=======================================
+ Hits         4519     4520    +1     
  Misses        119      119           
  Partials      113      113           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[alexdewar]

I've realised we still use the term capacity_a in the docs although I've changed the code to call it maximum_activity. Probably doesn't matter for now.

[tsmbland]

A couple of comments, otherwise looks good

[tsmbland]

I think cap2act is used in other energy systems models so we might consider keeping this. Maybe @ahawkes can comment?

[alexdewar]

Oh, interesting. I assumed it was a MUSE-ism. If spelling it out sounds silly to economists, then let's leave it as is.

We could always spell it out in the code and leave it abbreviated in the CSV column names if we wanted to.

[alexdewar]

@ahawkes do you have an opinion on this? It'd be good to get this PR merged in some form soonish so that we don't get merge conflicts.

[tsmbland]

Nope, no such thing as capacity_a in muse1

[alexdewar]

Oh ok. Is it just referred to as maximum activity or something?