Rails.logger should have level specified by config.log_level. 

Fix bug when log level of Rails.logger (which was set via config.logger) does not match the    config.log_level.
fix tests
update guide to reflect default HMAC SHA1 in MessageVerifier used in SignedCookieStore [ci skip]
remove language about configuring digest method [ci skip]
Minor optimization and code cleanup in query_methods.

- Use symbols rather than strings where possible to avoid extra object construction
- Use destructive methods where possible to avoid extra object construction
- Use array union rather than concat followed by uniq
- Use shorthand block syntax where possible
- Use consistent multiline block styles, method names, method parenteses style, and spacing
Added to 'Security' section; especially reference to 'Ruby on Rails Security Guide'. [ci skip]
Fix active_record_validations.md document, `:save` for `on:` validation helper was never available

According to the guide, ":save" value for the "on:" validation helper
was available like below

    validates :name, presence: true, on: :save

but this was never available according to the implementation of the
valid? method, which is below

    # Runs all the validations within the specified context. Returns
+true+ if
    # no errors are found, +false+ otherwise.
    #
    # If the argument is +false+ (default is +nil+), the context is set
to <tt>:create</tt> if
    # <tt>new_record?</tt> is +true+, and to <tt>:update</tt> if it is
not.
    #
    # Validations with no <tt>:on</tt> option will run no matter the
context. Validations with
    # some <tt>:on</tt> option will only run in the specified context.
    def valid?(context = nil)
      context ||= (new_record? ? :create : :update)
      output = super(context)
      errors.empty? && output
    end

So the documentation was always wrong since the PR proposed by
@neerajdotname  ( #10287 ) was rejected.
Merge pull request #11737 from tkhr/fix-document-about-on-validation-helpers

Fix active_record_validations.md document, `:save` for `on:` validation helper was never available
Merge pull request #11749 from Alamoz/getting_started_guide

Added to 'Security' section in 'Getting Started with Rails' guide, including reference to 'Ruby on Rails Security Guide'.
Merge pull request #11693 from egilburg/minor_relation_refactor

Minor optimization and code cleanup in query_methods.rb
Merge pull request #11677 from jaggederest/master

update guide to reflect default HMAC SHA1 in MessageVerifier used in SignedCookieStore
Merge pull request #11665 from mshytikov/fix-config-log_level

Rails.logger should have level specified by config.log_level.
Add CHANGELOG entry for #11665

[ci skip]
Pass assert_dom_equal message arg to underlying assertion

#assert_dom_equal and #assert_dom_not_equal both take a "failure"
message argument, but this argument was not utilized.
Merge pull request #11751 from rmm5t/assert_dom_equal-message

Pass assert_dom_equal message arg to underlying assertion