Allow regular expressions in postal codes

Programmers can take advantage of this feature when defining custom
default settings. And, since many CONSUL installations had custom
changes in the `custom/verification/residence.rb` model and those
changes might use regular expressions, we're making it easier to migrate
that code to the new system to define valid postal codes.

We aren't documenting this feature in the description in the admin
section because most administrators don't know what regular expressions
are.

Note that, in order to simplify the setting, we already define the `/\A`
and `\Z/` characters. So, if the custom code had something like
`postal_code =~ /^280/`, the setting would have to be "280*" (without
the quotes) or, in order to comply with a length validation,
"280[0-9]{2}" (without the quotes).

app/models/verification/residence.rb

@@ -110,7 +110,7 @@ class Verification::Residence
         if code_or_range.include?(":")
           Range.new(*code_or_range.split(":").map(&:strip)).include?(postal_code&.strip)
         else
-          postal_code&.strip == code_or_range.strip
+          /\A#{code_or_range.strip}\Z/.match?(postal_code&.strip)
         end
       end
     end

spec/models/verification/residence_spec.rb

@@ -126,6 +126,58 @@ describe Verification::Residence do
         expect(residence).to be_valid
       end
 
+      it "allows regular expressions" do
+        Setting["postal_codes"] = "007,[A-Za-z]{2}-[0-9]{3},86"
+
+        residence.postal_code = "007"
+        expect(residence).to be_valid
+
+        residence.postal_code = "86"
+        expect(residence).to be_valid
+
+        residence.postal_code = "AB-123"
+        expect(residence).to be_valid
+
+        residence.postal_code = "zz-789"
+        expect(residence).to be_valid
+
+        residence.postal_code = "006"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "87"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "AB-12"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "AB-1234"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "A-123"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "ABC-123"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "ABC-12"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "AB-A12"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "12A-12"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "123-12"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "ABC-A1"
+        expect(residence).not_to be_valid
+
+        residence.postal_code = "AB-123\n123"
+        expect(residence).not_to be_valid
+      end
+
       it "is not valid with postal codes not included in settings" do
         residence.postal_code = "12345"
         expect(residence).not_to be_valid