Price impact helper (v2)

[EndymionJkb]

Description

Intended as a replacement for #323, which is so far out-of-date it would be an unreadable diff if we tried to update it in place. Test doesn't pass; next step might be for the original author to look at this version. (I have very little context here.)

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Optimization: [ ] gas / [ ] bytecode
• Documentation or wording changes
• Other

Checklist:

• [N/A] The diff is legible and has no extraneous changes
• Complex code has been commented, including external interfaces
• Tests have 100% code coverage
• The base branch is either main, or there's a description of how to merge

Issue Resolution