Add gem "rails-erd"

.gitignore

@@ -25,6 +25,7 @@
 /.byebug_history
 /.rake_tasks~
 /coverage/
+/erd.pdf
 
 # Ignore master key for decrypting credentials and more.
 /config/master.key

Gemfile

@@ -134,6 +134,10 @@ group :development do
 
   # Makes spring watch files using the listen gem.
   gem 'spring-watcher-listen', '~> 2.0.0'
+
+  # Automatically generate an entity-relationship diagram (ERD)
+  # for your Rails models.
+  gem 'rails-erd', '~> 1.5'
 end
 
 group :test do

Gemfile.lock

@@ -88,6 +88,7 @@ GEM
     capybara-webkit (1.15.1)
       capybara (>= 2.3, < 4.0)
       json
+    choice (0.2.0)
     coderay (1.1.2)
     concurrent-ruby (1.1.3)
     coveralls (0.7.1)
@@ -230,6 +231,11 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
+    rails-erd (1.5.2)
+      activerecord (>= 3.2)
+      activesupport (>= 3.2)
+      choice (~> 0.2.0)
+      ruby-graphviz (~> 1.2)
     rails-html-sanitizer (1.0.4)
       loofah (~> 2.2, >= 2.2.2)
     rails-i18n (5.1.2)
@@ -280,6 +286,7 @@ GEM
       rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.4.0)
+    ruby-graphviz (1.2.4)
     ruby-progressbar (1.10.0)
     ruby_dep (1.5.0)
     sass (3.7.2)
@@ -383,6 +390,7 @@ DEPENDENCIES
   puma (~> 3.11)
   pundit (~> 2.0)
   rails (~> 5.2.1)
+  rails-erd (~> 1.5)
   rails-i18n (~> 5.1)
   rest-client (~> 2.0)
   rolify (~> 5.2)