[Fix #379] Mark Rails/DynamicFindBy as unsafe

Fixes #379.

This PR marks `Rails/DynamicFindBy` as unsafe.

CHANGELOG.md

@@ -26,6 +26,7 @@
 * [#444](https://github.com/rubocop/rubocop-rails/issues/444): Mark `Rails/Blank` as unsafe auto-correction. ([@koic][])
 * [#451](https://github.com/rubocop/rubocop-rails/issues/451): Make `Rails/RelativeDateConstant` aware of `yesterday` and `tomorrow` methods. ([@koic][])
 * [#454](https://github.com/rubocop/rubocop-rails/pull/454): Mark `Rails/WhereExists` as unsafe auto-correction. ([@koic][])
+* [#379](https://github.com/rubocop/rubocop-rails/issues/379): Mark `Rails/DynamicFindBy` as unsafe. ([@koic][])
 * [#456](https://github.com/rubocop/rubocop-rails/pull/456): Drop Ruby 2.4 support. ([@koic][])
 * [#462](https://github.com/rubocop/rubocop-rails/pull/462): Require RuboCop 1.7 or higher. ([@koic][])
 

config/default.yml

@@ -229,8 +229,9 @@ Rails/DynamicFindBy:
   Description: 'Use `find_by` instead of dynamic `find_by_*`.'
   StyleGuide: 'https://rails.rubystyle.guide#find_by'
   Enabled: true
+  Safe: false
   VersionAdded: '0.44'
-  VersionChanged: '2.6'
+  VersionChanged: '2.10'
   # The `Whitelist` has been deprecated, Please use `AllowedMethods` instead.
   Whitelist:
     - find_by_sql

docs/modules/ROOT/pages/cops_rails.adoc

@@ -1103,10 +1103,10 @@ delegate :foo, to: :bar, allow_nil: true
 | Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
 
 | Enabled
-| Yes
-| Yes
+| No
+| Yes (Unsafe)
 | 0.44
-| 2.6
+| 2.10
 |===
 
 This cop checks dynamic `find_by_*` methods.