In Relation#empty? use #exists? instead of #count.
Merge pull request #12533 from szimek/use_exists_in_relation_empty

In Relation#empty? use #exists? instead of #count.
Remove extra variable creation and merge.
Instrument the generation of Action Mailer messages

The processing of outbound mail is instrumented with the key
`process.action_mailer`. The payload includes the mailer name as well as
the mailer method.
Merge pull request #12556 from dasch/dasch/nstrument-am-processing

Instrument the generation of Action Mailer messages
Merge pull request #12591 from vipulnsward/remove_mail_merge

Remove extra variable creation and merge.
Raise an exception when model without primary key calls .find_with_ids
Merge pull request #12549 from makimoto/raise-when-find-without-pk

Raise an exception when model without primary key calls .find_with_ids
Allow unscope to work with `where.not`

Allows you to call #unscope on a relation with negative equality operators,
i.e. Arel::Nodes::NotIn and Arel::Nodes::NotEqual that have been generated
through the use of where.not.
Merge pull request #12565 from stormsilver/unscope_fixes

Allow unscope to work with `where.not`
remove trailing whitespace added with b057765 [ci skip].
Fix loading a sql structure file on postgres when the file's path has whitespace in it
Update docs on Tilt::Template in Asset Pipeline guide
Merge pull request #12603 from dv/fix-tilt-template-in-asset-pipeline-docs

Update docs on Tilt::Template in Asset Pipeline guide
Merge pull request #12567 from GoBoundless/fix_postgres_structure_import

Fix loading a sql structure file on postgres when the file's path has whitespace in it
Escape the parentheses in the default function regexp

This is causing every default value in PostreSQL database to being
handled as default function.

Fixes #12581