Add more descriptive "allowlist" terminology

This runs s/url_whitelist/url_allowlist/ and adds backwards-compatible
aliases for the terminology which can be easily deprecated or dropped
in the future, should that be desired.

README.markdown

@@ -342,11 +342,11 @@ DatabaseCleaner.allow_production = true
 DatabaseCleaner.allow_remote_database_url = true
 ```
 
-In Ruby, a URL whitelist can be specified. When specified, DatabaseCleaner will only allow `DATABASE_URL` to be equal
-to one of the values specified in the url whitelist like so:
+In Ruby, a URL allowlist can be specified. When specified, DatabaseCleaner will only allow `DATABASE_URL` to be equal
+to one of the values specified in the url allowlist like so:
 
 ```ruby
-DatabaseCleaner.url_whitelist = ['postgres://postgres@localhost', 'postgres://foo@bar']
+DatabaseCleaner.url_allowlist = ['postgres://postgres@localhost', 'postgres://foo@bar']
 ```
 
 ## COPYRIGHT

lib/database_cleaner/core.rb

@@ -14,7 +14,10 @@ module DatabaseCleaner
       :cleaning,
     ] => :cleaners
 
-    attr_accessor :allow_remote_database_url, :allow_production, :url_whitelist
+    attr_accessor :allow_remote_database_url, :allow_production, :url_allowlist
+
+    alias :url_whitelist :url_allowlist
+    alias :url_whitelist= :url_allowlist=
 
     def cleaners
       @cleaners ||= Cleaners.new

lib/database_cleaner/safeguard.rb

@@ -13,27 +13,27 @@ module DatabaseCleaner
         end
       end
 
-      class NotWhitelistedUrl < Error
+      class UrlNotAllowed < Error
         def initialize
-          super("ENV['DATABASE_URL'] is set to a URL that is not on the whitelist. Please refer to https://github.com/DatabaseCleaner/database_cleaner#safeguards")
+          super("ENV['DATABASE_URL'] is set to a URL that is not on the allowlist. Please refer to https://github.com/DatabaseCleaner/database_cleaner#safeguards")
         end
       end
     end
 
-    class WhitelistedUrl
+    class AllowedUrl
       def run
         return if skip?
-        raise Error::NotWhitelistedUrl if database_url_not_whitelisted?
+        raise Error::UrlNotAllowed if database_url_not_allowed?
       end
 
       private
 
-        def database_url_not_whitelisted?
-          !DatabaseCleaner.url_whitelist.include?(ENV['DATABASE_URL'])
+        def database_url_not_allowed?
+          !DatabaseCleaner.url_allowlist.include?(ENV['DATABASE_URL'])
         end
 
         def skip?
-          !DatabaseCleaner.url_whitelist
+          !DatabaseCleaner.url_allowlist
         end
     end
 
@@ -67,7 +67,7 @@ module DatabaseCleaner
         def skip?
           ENV['DATABASE_CLEANER_ALLOW_REMOTE_DATABASE_URL'] ||
             DatabaseCleaner.allow_remote_database_url ||
-            DatabaseCleaner.url_whitelist
+            DatabaseCleaner.url_allowlist
         end
     end
 
@@ -97,7 +97,7 @@ module DatabaseCleaner
     CHECKS = [
       RemoteDatabaseUrl,
       Production,
-      WhitelistedUrl
+      AllowedUrl
     ]
 
     def run

spec/database_cleaner/safeguard_spec.rb

@@ -72,13 +72,10 @@ module DatabaseCleaner
         end
       end
 
-      describe 'DatabaseCleaner.url_whitelist is set' do
-        let(:url_whitelist) { ['postgres://postgres@localhost', 'postgres://foo.bar'] }
+      describe 'DatabaseCleaner.url_allowlist is set' do
 
-        before { DatabaseCleaner.url_whitelist = url_whitelist }
-        after  { DatabaseCleaner.url_whitelist = nil }
-
-        describe 'A remote url is on the whitelist' do
+        shared_examples 'allowlist assigned' do
+          describe 'A remote url is on the allowlist' do
             let(:database_url) { 'postgres://foo.bar' }
 
             it 'does not raise' do
@@ -86,15 +83,15 @@ module DatabaseCleaner
             end
           end
 
-        describe 'A remote url is not on the whitelist' do
+          describe 'A remote url is not on the allowlist' do
             let(:database_url) { 'postgress://bar.baz' }
 
-          it 'raises a whitelist error' do
-            expect { cleaner.start }.to raise_error(Safeguard::Error::NotWhitelistedUrl)
+            it 'raises a allowlist error' do
+              expect { cleaner.start }.to raise_error(Safeguard::Error::UrlNotAllowed)
             end
           end
 
-        describe 'A local url is on the whitelist' do
+          describe 'A local url is on the allowlist' do
             let(:database_url) { 'postgres://postgres@localhost' }
 
             it 'does not raise' do
@@ -102,14 +99,30 @@ module DatabaseCleaner
             end
           end
 
-        describe 'A local url is not on the whitelist' do
+          describe 'A local url is not on the allowlist' do
             let(:database_url) { 'postgres://localhost' }
 
-          it 'raises a whitelist error' do
-            expect { cleaner.start }.to raise_error(Safeguard::Error::NotWhitelistedUrl)
+            it 'raises a not allowed error' do
+              expect { cleaner.start }.to raise_error(Safeguard::Error::UrlNotAllowed)
             end
           end
         end
+
+        let(:url_allowlist) { ['postgres://postgres@localhost', 'postgres://foo.bar'] }
+
+        describe 'url_allowlist' do
+          before { DatabaseCleaner.url_allowlist = url_allowlist }
+          after  { DatabaseCleaner.url_allowlist = nil }
+          it_behaves_like 'allowlist assigned'
+        end
+
+        describe 'url_whitelist' do
+          before { DatabaseCleaner.url_whitelist = url_allowlist }
+          after  { DatabaseCleaner.url_whitelist = nil }
+          it_behaves_like 'allowlist assigned'
+        end
+
+      end
     end
 
     describe 'ENV is set to production' do