Remove foreign key contraint in table job_warnings on 'fk_jobs_id'

The job_warnings table was created in a wrong way. There are two columns 'job_id' and 'fk_jobs_id'.
There is a foreign key constraint on 'fk_jobs_id', which references jobs(id).
CC coding never inserts data into 'fk_jobs_id', but only into 'job_id'.
So the foreign key constraint is not needed and causes way slower cleanup of pollable jobs,
which can even run into DB statement timeouts and cause an ever growing table.

db/migrations/20250116144231_remove_unnecessary_fk_in_job_warnings.rb

@@ -0,0 +1,7 @@
+Sequel.migration do
+  up do
+    alter_table :job_warnings do
+      drop_foreign_key :fk_jobs_id
+    end
+  end
+end

spec/migrations/20250116144231_remove_unnecessary_fk_in_job_warnings_spec.rb

@@ -0,0 +1,17 @@
+require 'spec_helper'
+require 'migrations/helpers/migration_shared_context'
+
+RSpec.describe "migration to remove foreign key constraint on table 'job_warnings' and column 'fk_jobs_id'", isolation: :truncation, type: :migration do
+  include_context 'migration' do
+    let(:migration_filename) { '20250116144231_remove_unnecessary_fk_in_job_warnings.rb' }
+  end
+
+  describe 'job_warnings table' do
+    it 'removed the fk constraint as well as the column' do
+      Sequel::Migrator.run(db, migrations_path, target: current_migration_index, allow_missing_migration_files: true)
+
+      expect(db.foreign_key_list(:job_warnings)).to be_empty
+      expect(db[:job_warnings].columns).not_to include(:fk_jobs_id)
+    end
+  end
+end