make a named volume for the Bety logs mountpoint

[infotroph]

Best I can tell nothing gets written to this, but because the Bety image specifies this path as a VOLUME, we were creating a new anonymous-but-permanent volume every time Compose spun up. Having one named one that stays empty seems a touch cleaner.

Description

Motivation and Context

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[robkooper]

probably should add this to the bety repo as well, just to be consistent.

[infotroph]

probably should add this to the bety repo as well, just to be consistent.

👍 Done in PecanProject/bety#762