One of the last places where we were using the old Tool model was the

"Repository Type" condition for integration configurations. This used

the BaseConditionModelMultipleChoice to show a multiple choice field

with the various registered repository types. This meant that the form

field was populated using the contents of the Tool table, and selected

values were stored as the primary keys of the selected Tool instances.
This change makes it so the RepositoryTypeChoice instead loads its

values from the new SCMTools registry, using the SCMTool ID as the key.

In order to handle any existing integration configurations, a new stage

has been added to the upgrade to look through existing integration

configurations and update them.

Created and edited integration configurations using various usage of

  the "Repository Type" choice. Saw that everything was loaded from and

  saved to the database correctly.
Created several integration configurations using the "Repository Type"

  choice and then ran the upgrade. Saw that old lists of integers

  (Tool PKs) were updated to be lists of strings corresponding to the

  correct SCMTool IDs.
Ran unit tests.