Removed confusing statement about adding route for show action in getting started guide [ci skip]

Free result_metadata directly instead of freeing 2nd, redundant call.

Create sqlite3 directory if not present

If the `db/` directory is not present on a remote machine it will blow up in unexpected ways with error messages that do not indicate there is a missing directory:

```
SQLite3::CantOpenException: unable to open database file
```

This PR checks to see if a directory exists for the sqlite3 file and if not creates it for you.

This PR is an alternative to #11692 as suggested by @josevalim

- routes for CRUD already exists as `resources :posts` is in
  `config/routes.rb`
- So we don't have to add any new route in the `config/routes.rb`
- As per #11644, the adding of routes which are already there confuses user, so here its
  changed to referring output of `rake routes`

`result_metadata` returns a new object each time it is called, so calling `result_metadata.free` is essentially a noop.  Instead call `free` directly on the metadata when we're done with it.

Passing the actual ID is not idiomatic.

Added data for permit array into scalar value

[ci skip]

Fix: documentation for ActiveModel::Errors [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.

[ci skip]

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

update guide to reflect default HMAC SHA1 in MessageVerifier used in SignedCookieStore

Minor optimization and code cleanup in query_methods.rb

Added to 'Security' section in 'Getting Started with Rails' guide, including reference to 'Ruby on Rails Security Guide'.

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.

We need to call `in_time_zone` to test that it isn't modifying the receiver
but since the variable isn't used it raises a warning so add an assertion
to make Ruby think it's being used.

The section was clearly wrong and was just an example about how to use ActiveSupport helpers in Rack/Sinatra

[ci skip]

[ci skip]

Add note that you must be in the rails app when starting the server

i18n guide update: corrected reference to activerecord to instead reference activemodel

This is a response to issue #11731 and is a common mistake for people
newer to rails that try forget to cd into the new rails app after
running rails new.

Removed an unnecessary loop - it kills performance on large texts.

[Fixes #11734]Correct Association Basics Guide on has_and_belongs_to_many

Changing the def self.table_name to self.table_name in the column_name.r...

used flat_map instead of map.flatten in /guides/rails_guides/helpers.rb

javascript_include_tag "extname" option for use by asset_path

fix for postgresql failing test in local

use flat_map