add proof of concept sftp downloader

Gemfile.lock

@@ -82,6 +82,7 @@ GEM
     ast (2.4.2)
     backport (1.2.0)
     bcrypt (3.1.18)
+    bcrypt_pbkdf (1.1.0)
     benchmark (0.2.1)
     better_html (2.0.1)
       actionview (>= 6.0)
@@ -131,6 +132,7 @@ GEM
     diff-lcs (1.5.0)
     docile (1.4.0)
     e2mmap (0.1.0)
+    ed25519 (1.3.0)
     erb_lint (0.3.1)
       activesupport
       better_html (>= 2.0.1)
@@ -207,8 +209,11 @@ GEM
       net-protocol
     net-protocol (0.2.1)
       timeout
+    net-sftp (4.0.0)
+      net-ssh (>= 5.0.0, < 8.0.0)
     net-smtp (0.3.3)
       net-protocol
+    net-ssh (7.0.1)
     newrelic_rpm (8.16.0)
     nio4r (2.5.8)
     nokogiri (1.14.2-x86_64-darwin)
@@ -413,6 +418,7 @@ PLATFORMS
 DEPENDENCIES
   activerecord-import
   apparition!
+  bcrypt_pbkdf
   bootsnap
   brakeman
   bullet
@@ -422,6 +428,7 @@ DEPENDENCIES
   database_cleaner
   debug
   devise
+  ed25519
   erb_lint
   erblint-github
   factory_bot_rails
@@ -433,6 +440,7 @@ DEPENDENCIES
   launchy
   listen (~> 3.0.5)
   nested_scaffold
+  net-sftp
   newrelic_rpm
   nokogiri (>= 1.13.4)
   omniauth