Allow searching by payment id

When reconciling payroll issues the ops team would like the ability to
search for claims by payment id, as this is what's in the payroll CSV.

app/models/claim/search.rb

@@ -26,7 +26,13 @@ def claims
         }
       }.flatten.map(&:id)
 
-      claim_match_query.or(Claim.where(eligibility_id: eligibility_ids))
+      claims_matched_on_payment_ids = Claim.joins(:payments).merge(
+        Payment.where(id: search_term)
+      )
+
+      claim_match_query
+        .or(Claim.where(eligibility_id: eligibility_ids))
+        .or(Claim.where(id: claims_matched_on_payment_ids))
     end
 
     private

spec/models/claim/search_spec.rb

@@ -115,4 +115,61 @@
       specify { expect(search.claims).to contain_exactly(claim, historical_matching_claim) }
     end
   end
+
+  context "search by payment id" do
+    let!(:claim_1) do
+      create(
+        :claim,
+        :submitted,
+        bank_account_number: "12345678",
+        bank_sort_code: "123456",
+        national_insurance_number: "QQ123456C"
+      )
+    end
+
+    let!(:claim_2) do
+      create(
+        :claim,
+        :submitted,
+        bank_account_number: "12345678",
+        bank_sort_code: "123456",
+        national_insurance_number: "QQ123456C"
+      )
+    end
+
+    let!(:claim_3) do
+      create(
+        :claim,
+        :submitted,
+        bank_account_number: "12345678",
+        bank_sort_code: "123456",
+        national_insurance_number: "QQ123456C"
+      )
+    end
+
+    let!(:claim_4) do
+      create(
+        :claim,
+        :submitted,
+        bank_account_number: "12345678",
+        bank_sort_code: "123456",
+        national_insurance_number: "QQ123456C"
+      )
+    end
+
+    let!(:payment_1) { create(:payment, claims: [claim_1, claim_2]) }
+
+    let!(:payment_2) do
+      create(:payment, claims: [claim_3], payroll_run: payment_1.payroll_run)
+    end
+
+    let(:query) { payment_1.id }
+
+    subject { search.claims }
+
+    it { is_expected.to include(:claim_1) }
+    it { is_expected.to include(:claim_2) }
+    it { is_expected.not_to include(:claim_3) }
+    it { is_expected.not_to include(:claim_4) }
+  end
 end