Insall "ed25519" gem to deploy with ed25519 SSH keys

Gemfile

@@ -87,6 +87,7 @@ group :development do
   # Necessary for elliptic curve SSH keys
   gem 'rbnacl', ">= 3.2", "<5.0"
   gem 'bcrypt_pbkdf', ">= 1.0", "<2.0"
+  gem 'ed25519', ">= 1.2", "< 2.0"
 end
 
 group :test do

Gemfile.lock

@@ -118,6 +118,7 @@ GEM
     devise-i18n (1.8.1)
       devise (>= 4.6)
     docile (1.3.2)
+    ed25519 (1.2.4)
     erubi (1.8.0)
     execjs (2.7.0)
     factory_bot (5.0.2)
@@ -382,6 +383,7 @@ DEPENDENCIES
   database_cleaner
   devise (~> 4.7)
   devise-i18n (~> 1.8)
+  ed25519 (>= 1.2, < 2.0)
   factory_bot_rails (~> 5.0)
   guard
   guard-minitest
@@ -390,7 +392,6 @@ DEPENDENCIES
   jbuilder (~> 2.7)
   kaminari
   launchy
-  letter_opener
   letter_opener_web
   listen (>= 3.0.5, < 3.2)
   logging