Extract additions/removals from slicing
Extract additions/removals from slicing

Refactor for simplification that makes a future change easier

refs INTEROP-6715

flag=microsoft_group_enrollments_syncing

test plan: the specs pass, existing coverage is sufficient

Change-Id: Ieb1ddbee9788ec6651c2f2b618261987c4b7d66f
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/268756
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Tucker Mcknight <4b51b98c1d84aa97854d216bd061ce5d3eda8a28@instructure.com>
Reviewed-by: Evan Battaglia <e557ffdfc4b80aab44858030b0ae5370b86cb7b1@instructure.com>
QA-Review: Tucker Mcknight <4b51b98c1d84aa97854d216bd061ce5d3eda8a28@instructure.com>
Product-Review: Sean Scally <ceb34b930afeb707ad0575cfce0e31dce3c15014@instructure.com>

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