Add some more validation checks for process flows

[alexdewar]

Description

I've added some extra validation steps related to process flows, namely:

• Check that process flows are valid numbers
• Check that flow costs are valid numbers
• Check that every process has at least one associated process flow (i.e. it produces or consumes something)
• Disallow commodity flexible flows for now (we will only support fixed ones for now)

I also added a check that every process has at least one PAC.

Closes #277. Closes #278. Closes #279.

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

Attention: Patch coverage is 95.65217% with 9 lines in your changes missing coverage. Please review.

Project coverage is 95.56%. Comparing base (1d8072a) to head (d4fca15).
Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
src/input/process.rs	95.80%	0 Missing and 6 partials ⚠️
src/input/process/availability.rs	77.77%	0 Missing and 2 partials ⚠️
src/input/process/flow.rs	98.18%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #323      +/-   ##
==========================================
+ Coverage   95.29%   95.56%   +0.27%     
==========================================
  Files          26       26              
  Lines        2613     2751     +138     
  Branches     2613     2751     +138     
==========================================
+ Hits         2490     2629     +139     
  Misses         47       47              
+ Partials       76       75       -1     

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[AdrianDAlessandro]

LGTM!

[AdrianDAlessandro]

Should we add tests for these two cases?

[alexdewar]

Yes, probably. I was being a bit lazy here.

[alexdewar]

In order to write tests, I split out the map creation stuff into its own function. I also figured that this function is the right place to check for other missing process data (e.g. flows, availabilities). I had been checking for this by just checking that the data structures had the same length as the process_ids one, but by doing the check when we actually need the data for a given process, we can tell the user which process is missing this data, so I think that's an improvement.

[AdrianDAlessandro]

Why the name change here? As far as I can tell, it is still a ProcessFlowRaw that is being iterated over.

[alexdewar]

I thought it was more readable that way... Maybe not though

[AdrianDAlessandro]

Maybe explain the restriction on the value in this message?

[alexdewar]

I've made a separate check for zero values instead, because I think that's the one that's likely to trip users up. If they put nan as a value for flow, we probably don't need to explain why that's not allowed!