Upgrade to Rails 6.1

Note that `Capybara.app_host` now returns `nil` by default and that
breaks tests using `lvh.me` or our custom `app_host` method, so we're
setting `Capybara.app_host` to the value it had in earlier versions of
Rails. I also haven't found a way to remove the code to set the
integration session host in relationable tests which I mentioned in
commit ffc14e499.

Also note that we now filter more parameters, and that they match
regular expressions, so filtering `:passw` means we're filtering
`passwd`, `password`, ...

config/initializers/backtrace_silencers.rb

@@ -1,7 +1,8 @@
 # Be sure to restart your server when you modify this file.
 
 # You can add backtrace silencers for libraries that you're using but don't wish to see in your backtraces.
-# Rails.backtrace_cleaner.add_silencer { |line| line =~ /my_noisy_library/ }
+# Rails.backtrace_cleaner.add_silencer { |line| /my_noisy_library/.match?(line) }
 
-# You can also remove all the silencers if you're trying to debug a problem that might stem from framework code.
-# Rails.backtrace_cleaner.remove_silencers!
+# You can also remove all the silencers if you're trying to debug a problem that might stem from framework code
+# by setting BACKTRACE=1 before calling your invocation, like "BACKTRACE=1 ./bin/rails runner 'MyClass.perform'".
+Rails.backtrace_cleaner.remove_silencers! if ENV["BACKTRACE"]

config/initializers/filter_parameter_logging.rb

@@ -1,4 +1,6 @@
 # Be sure to restart your server when you modify this file.
 
 # Configure sensitive parameters which will be filtered from the log file.
-Rails.application.config.filter_parameters += [:password]
+Rails.application.config.filter_parameters += [
+  :passw, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn
+]

config/initializers/new_framework_defaults_6_1.rb

@@ -0,0 +1,67 @@
+# Be sure to restart your server when you modify this file.
+#
+# This file contains migration options to ease your Rails 6.1 upgrade.
+#
+# Once upgraded flip defaults one by one to migrate to the new default.
+#
+# Read the Guide for Upgrading Ruby on Rails for more info on each option.
+
+# Support for inversing belongs_to -> has_many Active Record associations.
+# Rails.application.config.active_record.has_many_inversing = true
+
+# Track Active Storage variants in the database.
+# Rails.application.config.active_storage.track_variants = true
+
+# Apply random variation to the delay when retrying failed jobs.
+# Rails.application.config.active_job.retry_jitter = 0.15
+
+# Stop executing `after_enqueue`/`after_perform` callbacks if
+# `before_enqueue`/`before_perform` respectively halts with `throw :abort`.
+# Rails.application.config.active_job.skip_after_callbacks_if_terminated = true
+
+# Specify cookies SameSite protection level: either :none, :lax, or :strict.
+#
+# This change is not backwards compatible with earlier Rails versions.
+# It's best enabled when your entire app is migrated and stable on 6.1.
+# Rails.application.config.action_dispatch.cookies_same_site_protection = :lax
+
+# Generate CSRF tokens that are encoded in URL-safe Base64.
+#
+# This change is not backwards compatible with earlier Rails versions.
+# It's best enabled when your entire app is migrated and stable on 6.1.
+# Rails.application.config.action_controller.urlsafe_csrf_tokens = true
+
+# Specify whether `ActiveSupport::TimeZone.utc_to_local` returns a time with an
+# UTC offset or a UTC time.
+# ActiveSupport.utc_to_local_returns_utc_offset_times = true
+
+# Change the default HTTP status code to `308` when redirecting non-GET/HEAD
+# requests to HTTPS in `ActionDispatch::SSL` middleware.
+# Rails.application.config.action_dispatch.ssl_default_redirect_status = 308
+
+# Use new connection handling API. For most applications this won't have any
+# effect. For applications using multiple databases, this new API provides
+# support for granular connection swapping.
+# Rails.application.config.active_record.legacy_connection_handling = false
+
+# Make `form_with` generate non-remote forms by default.
+# Rails.application.config.action_view.form_with_generates_remote_forms = false
+
+# Set the default queue name for the analysis job to the queue adapter default.
+# Rails.application.config.active_storage.queues.analysis = nil
+
+# Set the default queue name for the purge job to the queue adapter default.
+# Rails.application.config.active_storage.queues.purge = nil
+
+# Set the default queue name for the incineration job to the queue adapter default.
+# Rails.application.config.action_mailbox.queues.incineration = nil
+
+# Set the default queue name for the routing job to the queue adapter default.
+# Rails.application.config.action_mailbox.queues.routing = nil
+
+# Set the default queue name for the mail deliver job to the queue adapter default.
+# Rails.application.config.action_mailer.deliver_later_queue_name = nil
+
+# Generate a `Link` header that gives a hint to modern browsers about
+# preloading assets when using `javascript_include_tag` and `stylesheet_link_tag`.
+# Rails.application.config.action_view.preload_links_header = true

config/initializers/permissions_policy.rb

@@ -0,0 +1,11 @@
+# Define an application-wide HTTP permissions policy. For further
+# information see https://developers.google.com/web/updates/2018/06/feature-policy
+#
+# Rails.application.config.permissions_policy do |f|
+#   f.camera      :none
+#   f.gyroscope   :none
+#   f.microphone  :none
+#   f.usb         :none
+#   f.fullscreen  :self
+#   f.payment     :self, "https://secure.example.com"
+# end