[Fire162]

Description

Implements state_backwards and database_backwards for CreatePhoneDevice and sets reversible = True so the phonenumber app migration can be rolled back to zero.

Motivation and Context

Closes #780. Allows projects to migrate the phonenumber app to zero when uninstalling or removing phone device support.

How Has This Been Tested?

Added regression test in tests/test_migrations.py validating migrating phonenumber to zero and back, and ran the test suite.

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 code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[moggers87]

Closing this as it appears to be duplicate of #803