Encrypt application settings with pre and post deployments

We had concerns about the cached values on Redis with the previous two
releases strategy:

First release (this commit):
  - Create new encrypted fields in the database.
  - Start populating new encrypted fields, read the encrypted fields or
    fallback to the plaintext fields.
  - Backfill the data removing the plaintext fields to the encrypted
    fields.
Second release:
  - Remove the virtual attribute (created in step 2).
  - Drop plaintext columns from the database (empty columns after
    step 3).

We end up with a better strategy only using migration scripts in one
release:
  - Pre-deployment migration: Add columns required for storing encrypted
    values.
  - Pre-deployment migration: Store the encrypted values in the new
    columns.
  - Post-deployment migration: Remove the old unencrypted columns

1 files changed, 0 insertions, 6 deletions

diff --git a/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb b/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb
index d7abb29fd75..e6b9a40ad4f 100644
--- a/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb
+++ b/db/migrate/20191120115530_encrypt_plaintext_attributes_on_application_settings.rb
@@ -70,12 +70,6 @@ class EncryptPlaintextAttributesOnApplicationSettings < ActiveRecord::Migration[
         end
       )
       application_setting.save(validate: false)
-
-      application_setting.update_columns(
-        PLAINTEXT_ATTRIBUTES.each_with_object({}) do |plaintext_attribute, attributes|
-          attributes[plaintext_attribute] = nil
-        end
-      )
     end
   end