Use strip_heredoc where possible

Following up on an observation by @rafaelfranca

https://github.com/rails/rails/pull/10170/files#r3753963

Reduce the number of gsub calls to the two cases where inputs are concatenated
from various sources and with inconsistent indentation.

Also zap extraneous spacing from the sass-rails line... presumably this is a
holdover from a previous time where this aligned the version string with an
adjacent line.
added a test suite for the postgres binary type
this shows a problem with nil values
fix for the bytea/binary nil value bug
Document collection.create! on has_many associations in ActiveRecord
Merge pull request #10212 from mariovisic/active_record_doc

Add documentation for `collection.create!` on has_many records. [ci skip]
interpolate instead of string concat
Merge pull request #10220 from vipulnsward/interpolate_on_string

interpolate instead of string concat
Merge pull request #10214 from mattetti/ar_postgres_bytea

AR postgres binary bug fix
Merge pull request #10178 from rubys/app_base_strip_heredoc

Use strip_heredoc where possible
Revert "fixing bit string test"

This reverts commit cdd293cb963b895ff580eb20d10f5d56ecb3d447.

Reason: This wasn't properly fix.
Add OID::Bit for supporting bit string.
Merge pull request #10225 from kennyj/fix_bit_string_problem

Fix bit string problem
asset guide, match application.rb snippets to the generated file [ci skip]

`if defined?(Bundler)` is no longer used in our current application.rb