Fix org_participation role

This enum stores the values as integers and maps them to symbols for
ease. We have also declared is as a string, which is both incorrect and
broken in Rails 7.

In Rails 7 we can declare a default inside the enum definition, so we do
that.

We think this is working now because all records are 'implementing/3' so
any loaded model returns the string `implementing` by default.

We've check the production database and all values are correctly set to
the integer '3'.

app/models/org_participation.rb

@@ -2,15 +2,13 @@ class OrgParticipation < ApplicationRecord
   belongs_to :activity
   belongs_to :organisation
 
-  attribute :role, :string, default: "implementing"
-
-  enum role: {
+  enum :role, {
     partner_organisation: 0,
     matched_effort_provider: 1,
     external_income_provider: 2,
     implementing: 3,
     service_owner: 99
-  }
+  }, default: :implementing
 
   scope :implementing, -> { where(role: :implementing) }
 

spec/models/org_participation_spec.rb

@@ -45,4 +45,12 @@
       end
     end
   end
+
+  describe "the default role" do
+    it "is implementing" do
+      subject = OrgParticipation.new
+
+      expect(subject.implementing?).to be true
+    end
+  end
 end