Import story priority as Priority custom field values

[semperos]

The Shortcut Priority Custom Field is enabled in all new workspaces by default.

A previous commit introduced the initialization routines to populate a local data/priorities.csv file that includes a mapping from Pivotal priority to the Priority Custom Field in Shortcut.

This commit leverages that mapping to enhance imported Shortcut Stories with a Priority custom field value.

Pivotal priority p0 through p3 are mapping to the Priority Custom Field Values in Shortcut with positions 0 through 3 (commonly named "Highest", "High", "Medium", and "Low", though users are free to rename them). Pivotal priority of "none" is considered a signal not to set the Priority field in Shortcut at all, so that value is ignored during import.

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⭐ For the PR reviewer:

• I alphabetized a few different lists of names
• See pivotal_import_test.py to understand the data shapes in play
• I've tested this against a test Production workspace. You can do the same by running:
  • make clean import to ensure a dry-run works
  • make import-apply to import Stories/Epics/etc.
  • make delete-apply to delete those imported entities

[shortcut-integration]

This pull request has been linked to Shortcut Story #264493: Import story priority.

[laurenarnett]

This looks good, looking at the tests definitely helped with understanding how the priority_config is being used for translation.