Simplify unless conditional with OR
Get rid of conditional since column_for handles raising now

column_for will raise in case column is not found for the given table,
so there is no need to handle that here.
Simplify building options hash in rename column method for mysql
Use the reader attribute rather than the instance var when possible
Fix examples indent and improve #process docs a bit [ci skip]
Convert column name to string only once
Remove deprecated file(`active_support/core_ext/object/to_json.rb`) and its test case.
Follow-up to #14905 and formatting pass

on the Getting Started guide.

[skip ci]

Added 2 changes suggested by @robin850 [skip ci]
Merge pull request #14961 from jonatack/patch-7

Follow-up to #14905 and formatting pass [ci skip]
Merge pull request #14974 from kuldeepaggarwal/remove-deprecated-files

Remove deprecated file
Merge pull request #14973 from kuldeepaggarwal/f-refactor

Convert column name to string only once
Merge pull request #14946 from jcoleman/fix-null-binary-column-logging-exception

Fix exception when logging SQL w/ nil binary value.

Conflicts:
	activerecord/CHANGELOG.md
Invert the if/else clause

The case where the value is present is more common
Merge pull request #14949 from bogdan/empty-hash-array-parameterization

[Fixes #14948] Hash#to_query: right serialization for  empty hash and array
No need the else clause
Improve CHANGELOG [ci skip]
Merge pull request #11166 from xavier/callable_constraint_verification

Callable route constraint verification

Conflicts:
	actionpack/CHANGELOG.md
Do not use short-circuit return
Use assert_raises
Improve CHANGELOG entry