This also adds a new column, message_checksum, to the action_mailbox_inbound_emails table
for storing SHA1 digest of the email source. Additionally, it makes generating the missing
message id deterministic and adds a unique index on message_checksum and message_id to
detect duplicate emails.
- config.load_defaults 6.0 in the dummy app and
fix the test since by default rails 6.0 configured
does not generate "utf8" hidden input, see #32125
- Use `ActiveRecord::Migration[6.0]` in the dummy app
since actiontext will be since Rails 6.0
- Fix `CreateActiveStorageTables` migration in the dummy app.
Add `t.foreign_key :active_storage_blobs, column: :blob_id`
It was added in 2ae3a29508.
- `rails/actiontext$ yarn install`
Since Action Mailbox will be introduced in Rails 6.0,
it makes more sense to generate migration of that version.
Also I changed its test dummy app to use default 6.0 configs.
