tests for merging Relations of different classes.
fix weird Emacs auto indentation. [ci skip]
Merge pull request #12772 from dmathieu/no_touching

Add No Touching
Make it clear that require 'active_support' is required [ci-skip]
Merge pull request #12874 from chancancode/better_as_loading_guides

Make it clear that require 'active_support' is required [ci-skip]
Use rescue with a splat rather and catching all and filtering
Merge pull request #12882 from charliesome/use-rescue-splat-in-suppress

Use rescue with a splat rather and catching all exceptions and manually filtering in Kernel#suppress
Updated guides link for 3.2.x to latest stable version 3.2.15 [skip-ci]
Get rid of unused  variable
Merge pull request #12883 from Amit-Thawait/master

Updated guides link for 3.2.x to latest stable version 3.2.15 [ci skip]
Merge pull request #12845 from amatsuda/should_ar_depend_on_rails

Refer to Rails.env from AR only when Rails is defined
Ruby's new Hash syntax applied in actionmailer
Merge pull request #12884 from akshay-vishnoi/refactor

Ruby's new Hash syntax applied in actionmailer
Merge pull request #12832 from vipulnsward/move_schema_creation

Move `SchemaCreation` to its own file instead of `AbstractAdapter`.
Clean up `require ‘active_support/deprecation’` and remove circular require
Merge pull request #12861 from route/missed_require_for_module

Clean up `require ‘active_support/deprecation’` and remove circular require
#presence used
Merge pull request #12886 from akshay-vishnoi/refactor

#presence used
Add AR::Base.to_param for convenient "pretty" URLs derived from a model's attribute or method.
class methods moved to already defined class<<self block