continuation of PR #8161 Display error notification when attempting to purchase invalid amount of gems - fixes #8145 (#8688)

* Translation string for error notification

* Use function instead of a link for paypal

* Inject notification service, function to check the amount of gems to purchase, function to handle payments with paypal

* Throw error if amount of gems is zero or negative

* Add condition to raise error if amount is negative

* Added gem errors for gifts 0 or less

* Fixed linting and broken test

* Fixed test syntax

* Added back needed strings

* Fixed group locales

test/api/v3/unit/libs/stripePayments.test.js

@@ -48,7 +48,36 @@ describe('Stripe Payments', () => {
       payments.createSubscription.restore();
     });
 
+    it('should error if gem amount is too low', async () => {
+      let receivingUser = new User();
+      receivingUser.save();
+      gift = {
+        type: 'gems',
+        gems: {
+          amount: 0,
+          uuid: receivingUser._id,
+        },
+      };
+
+      await expect(stripePayments.checkout({
+        token,
+        user,
+        gift,
+        groupId,
+        email,
+        headers,
+        coupon,
+      }, stripe))
+      .to.eventually.be.rejected.and.to.eql({
+        httpCode: 400,
+        message: 'Amount must be at least 1.',
+        name: 'BadRequest',
+      });
+    });
+
     it('should purchase gems', async () => {
+      gift = undefined;
+
       await stripePayments.checkout({
         token,
         user,