*   Only warn about negative enums if a positive form that would cause conflicts exists.

    Fixes #39065.

    *Alex Ghiculescu*

*   Add option to run `default_scope` on all queries.

    Previously, a `default_scope` would only run on select or insert queries. In some cases, like non-Rails tenant sharding solutions, it may be desirable to run `default_scope` on all queries in order to ensure queries are including a foreign key for the shard (ie `blog_id`).

    Now applications can add an option to run on all queries including select, insert, delete, and update by adding an `all_queries` option to the default scope definition.

    ```ruby
    class Article < ApplicationRecord
      default_scope -> { where(blog_id: Current.blog.id) }, all_queries: true
    end
    ```

    *Eileen M. Uchitelle*

*   Add `where.associated` to check for the presence of an association.

    ```ruby
    # Before:
    account.users.joins(:contact).where.not(contact_id: nil)

    # After:
    account.users.where.associated(:contact)
    ```

    Also mirrors `where.missing`.

    *Kasper Timm Hansen*

*   Allow constructors (`build_association` and `create_association`) on
    `has_one :through` associations.

    *Santiago Perez Perret*


Please check [6-1-stable](https://github.com/rails/rails/blob/6-1-stable/activerecord/CHANGELOG.md) for previous changes.