Updating valid domain registration (#15436)

* Updating valid domain registration

Prior to this commit, our regular expression did not account for the `-`
character as valid within the domain.  The `-` character cannot be the
first nor last character of the domain (e.g. `-hello.com` nor
`hello-.com` are invalid but `hell-o.com` is valid).

In addition I tidied up the default value of the
`blocked_registration_email_domains` to match it's sibling `allowed_registration_email_domains`.

This relates to the spammer seo-hunt.com

* Adding validator domain validator spec

* Moving request spec to unit spec

This change does two things:

1) Allows for 2 character domains
2) Moves the spec for 2 character domains from an expensive spec to a
   cheaper to run spec (e.g., request-cycle to unit-test validator)

It preserves PR #12268

app/models/settings/authentication.rb

@@ -11,7 +11,7 @@ module Settings
     setting :apple_key_id, type: :string
     setting :apple_pem, type: :string
     setting :apple_team_id, type: :string
-    setting :blocked_registration_email_domains, type: :array, default: %(), validates: {
+    setting :blocked_registration_email_domains, type: :array, default: %w[], validates: {
       valid_domain_csv: true
     }
     setting :display_email_domain_allow_list_publicly, type: :boolean, default: false

app/validators/valid_domain_csv_validator.rb

@@ -1,6 +1,10 @@
+# @note While the validator implies a CSV, the implementation is that
+#       we have an array.  Upstream implementors likely accept a CSV
+#       and coerce it into an array.  See Authentication::Base for an
+#       example of coercing the CSV into an array.
 class ValidDomainCsvValidator < ActiveModel::EachValidator
   DEFAULT_MESSAGE = "must be a comma-separated list of valid domains".freeze
-  VALID_DOMAIN = /^[a-zA-Z0-9]{1,61}[a-zA-Z0-9](?:\.[a-zA-Z]{2,})+$/
+  VALID_DOMAIN = /^[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9](?:\.[a-zA-Z]{2,})+$/
 
   def validate_each(record, attribute, value)
     return unless value

spec/requests/admin/configs_spec.rb

@@ -113,14 +113,6 @@ RSpec.describe "/admin/customization/config", type: :request do
           expect(Settings::Authentication.allowed_registration_email_domains).to eq(%w[dev.to forem.com forem.dev])
         end
 
-        it "allows 2-character domains" do
-          proper_list = "dev.to, forem.com, 2u.com"
-          post admin_settings_authentications_path, params: {
-            settings_authentication: { allowed_registration_email_domains: proper_list }
-          }
-          expect(Settings::Authentication.allowed_registration_email_domains).to eq(%w[dev.to forem.com 2u.com])
-        end
-
         it "does not allow improper domain list" do
           impproper_list = "dev.to, foremcom, forem.dev"
           post admin_settings_authentications_path, params: {

spec/validators/valid_domain_csv_validator_spec.rb

@@ -0,0 +1,41 @@
+require "rails_helper"
+
+RSpec.describe ValidDomainCsvValidator do
+  let(:validatable) do
+    Class.new do
+      def self.name
+        "Validatable"
+      end
+      include ActiveModel::Validations
+      attr_accessor :domains
+
+      validates :domains, valid_domain_csv: true
+    end
+  end
+  let(:model) { validatable.new }
+
+  it "marks valid a domain with dashes in the middle" do
+    model.domains = ["seo-hunt.com"]
+    expect(model).to be_valid
+  end
+
+  it "marks valid a two character domain" do
+    model.domains = ["2u.com"]
+    expect(model).to be_valid
+  end
+
+  it "marks invalid a domain with a dash as a prefix" do
+    model.domains = ["-seo-hunt.com"]
+    expect(model).to be_invalid
+  end
+
+  it "marks valid an array of domains" do
+    model.domains = ["hello.com", "world.org"]
+    expect(model).to be_valid
+  end
+
+  it "marks invalid an array of domains if one is invalid" do
+    model.domains = ["hello.com", "world.org", "notadomain"]
+    expect(model).to be_invalid
+  end
+end