- Tests on Travis are randomly failing because schema_migrations table
does not exist in teardown block.
- Also checked that all other places where we have used
`ActiveRecord::SchemaMigration.delete_all` we have rescued it, so used
it here also. This failure was not specifically related to the test
added in this PR but to overall compatibility migration tests, so
adding as separate commit.
- Using `references` or `belongs_to` in migrations will always add index
for the referenced column by default, without adding `index:true` option
to generated migration file.
- Users can opt out of this by passing `index: false`.
- Legacy migrations won't be affected by this change. They will continue
to run as they were before.
- Fixes#18146
