There is an issue with the GORM auto-migration, in that it doesn't
always disable foreign key constraints when it should. Due to
limitations of SQLite, not all 'alter table' commands you'd want to use
are available. As a workaround, these steps are performed:
1. create a new table with the desired schema,
2. copy the data over,
3. drop the old table,
4. rename the new table to the old name.
Step #3 will wreak havoc with the database when foreign key constraint
checks are active, so no we temporarily deactivate them while performing
database migration.
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