Ensure conditional answers are removed on funding page

Use the `onSave` hook to remove conditional answers when the parent
answer changes.

server/form-pages/apply/area-and-funding/funding-information/fundingCas2Accommodation.test.ts

@@ -75,4 +75,30 @@ describe('FundingCas2Accommodation', () => {
       })
     })
   })
+
+  describe('onSave', () => {
+    it('should remove conditional answers if the answers are no longer relevant', () => {
+      const page = new FundingCas2Accommodation(
+        {
+          fundingSource: 'benefits',
+          fundingSourceDetail: 'Funding source details',
+          hasNationalInsuranceNumber: 'no',
+          nationalInsuranceNumber: 'SF123456X',
+          receivingBenefits: 'no',
+          receivedBenefitSanctions: 'yes',
+          inEducationOrTraining: 'yes',
+        },
+        application,
+      )
+
+      page.onSave()
+
+      expect(page.body).toEqual({
+        fundingSource: 'benefits',
+        hasNationalInsuranceNumber: 'no',
+        receivingBenefits: 'no',
+        inEducationOrTraining: 'yes',
+      })
+    })
+  })
 })

server/form-pages/apply/area-and-funding/funding-information/fundingCas2Accommodation.ts

@@ -97,4 +97,16 @@ export default class FundingCas2Accommodation implements TaskListPage {
 
     return [{ ...yes, conditional: { html: conditionalHtml } }, ...items, { ...dontKnow }]
   }
+
+  onSave() {
+    if (this.body.fundingSource === 'benefits') {
+      delete this.body.fundingSourceDetail
+    }
+    if (this.body.hasNationalInsuranceNumber === 'no') {
+      delete this.body.nationalInsuranceNumber
+    }
+    if (this.body.receivingBenefits === 'no') {
+      delete this.body.receivedBenefitSanctions
+    }
+  }
 }