Use letter_opener for dev environment

Gemfile

@@ -59,6 +59,7 @@ group :development, :staging do
   gem 'better_errors'
   gem 'binding_of_caller'
   gem 'bootsnap', require: false
+  gem 'letter_opener'
   gem 'listen'
   gem 'pry-rails'
   gem 'rack-mini-profiler'

Gemfile.lock

@@ -219,6 +219,10 @@ GEM
     kaminari-core (1.2.2)
     kramdown (2.4.0)
       rexml
+    launchy (2.5.0)
+      addressable (~> 2.7)
+    letter_opener (1.8.1)
+      launchy (>= 2.2, < 3)
     listen (3.7.1)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
@@ -566,6 +570,7 @@ DEPENDENCIES
   js-routes
   json_schemer
   kramdown
+  letter_opener
   listen
   mimemagic
   mnemosyne-ruby

config/environments/development.rb

@@ -38,6 +38,10 @@ Rails.application.configure do
   config.active_storage.service = :local
 
   # Don't care if the mailer can't send.
+  config.action_mailer.perform_deliveries = true
+
+  # Perform deliveries via letter opener
+  config.action_mailer.delivery_method = :letter_opener
   config.action_mailer.raise_delivery_errors = false
 
   config.action_mailer.perform_caching = false