Change mutation to query amount and memo, check in test that amount and memo have the right values.

backend/src/graphql/resolver/ContributionResolver.test.ts

@@ -110,7 +110,10 @@ describe('ContributionResolver', () => {
           ).resolves.toEqual(
             expect.objectContaining({
               data: {
-                createContribution: true,
+                createContribution: {
+                  amount: '100',
+                  memo: 'Test env contribution',
+                },
               },
             }),
           )

backend/src/seeds/graphql/mutations.ts

@@ -233,6 +233,9 @@ export const deleteContributionLink = gql`
 
 export const createContribution = gql`
   mutation ($amount: Decimal!, $memo: String!, $creationDate: String!) {
-    createContribution(amount: $amount, memo: $memo, creationDate: $creationDate)
+    createContribution(amount: $amount, memo: $memo, creationDate: $creationDate) {
+      amount
+      memo
+    }
   }
 `