Add missing postgres gem

Needed in production

Gemfile

@@ -3,8 +3,6 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 6.0.3', '>= 6.0.3.4'
-# Use sqlite3 as the database for Active Record
-gem 'sqlite3', '~> 1.4'
 # Use Puma as the app server
 gem 'puma', '~> 4.1'
 # Use SCSS for stylesheets
@@ -31,6 +29,8 @@ gem 'devise_ldap_authenticatable'
 gem 'net-ldap'
 
 group :development, :test do
+  # Use sqlite3 as the database for Active Record
+  gem 'sqlite3', '~> 1.4'
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
 end
@@ -53,5 +53,9 @@ group :test do
   gem 'database_cleaner'
 end
 
+group :production do
+  # Use postgresql as the database for Active Record
+  gem 'pg', '~> 1.2.3'
+end
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]