fix: attempt a react friendly fix of summing (#7151)

## About the changes

Summing on Billing page got a little wonky after changing how the
summing worked when the estimation flag is off. This attempts to return
it to previous way of showing numbers when flag is off

If you go directly to the billing page it will not add user calculations
to the total. If you however interact with the UI, like change tabs back
and forth, it will suddenly show the correct sum:


![image](https://github.com/Unleash/unleash/assets/707867/af6eeddf-be3f-42ae-a588-f57c30d739ca)


![image](https://github.com/Unleash/unleash/assets/707867/b4a0b832-a550-4e87-aa69-7b27f96d3beb)

---------

Co-authored-by: Nuno Góis <github@nunogois.com>
Co-authored-by: Gastón Fournier <gaston@getunleash.io>

.github/workflows/build_frontend_prs.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    name: build
     defaults:
       run:
         working-directory: frontend

frontend/src/component/admin/billing/BillingDashboard/BillingPlan/BillingPlan.tsx

@@ -1,5 +1,5 @@
 import type { FC } from 'react';
-import { useState, useEffect } from 'react';
+import { useMemo } from 'react';
 import { Alert, Divider, Grid, styled, Typography } from '@mui/material';
 import { Link } from 'react-router-dom';
 import CheckIcon from '@mui/icons-material/Check';
@@ -16,9 +16,9 @@ import { GridRow } from 'component/common/GridRow/GridRow';
 import { GridCol } from 'component/common/GridCol/GridCol';
 import { Badge } from 'component/common/Badge/Badge';
 import { GridColLink } from './GridColLink/GridColLink';
-import { useInstanceTrafficMetrics } from 'hooks/api/getters/useInstanceTrafficMetrics/useInstanceTrafficMetrics';
 import { useTrafficDataEstimation } from 'hooks/useTrafficData';
 import { useUiFlag } from 'hooks/useUiFlag';
+import { useInstanceTrafficMetrics } from 'hooks/api/getters/useInstanceTrafficMetrics/useInstanceTrafficMetrics';
 
 const StyledPlanBox = styled('aside')(({ theme }) => ({
     padding: theme.spacing(2.5),
@@ -78,9 +78,9 @@ interface IBillingPlanProps {
 const proPlanIncludedRequests = 53_000_000;
 
 export const BillingPlan: FC<IBillingPlanProps> = ({ instanceStatus }) => {
-    const { users } = useUsers();
+    const { users, loading } = useUsers();
     const expired = trialHasExpired(instanceStatus);
-    const { uiConfig, isPro } = useUiConfig();
+    const { isPro } = useUiConfig();
 
     const {
         currentPeriod,
@@ -104,37 +104,39 @@ export const BillingPlan: FC<IBillingPlanProps> = ({ instanceStatus }) => {
 
     const planPrice = price[instanceStatus.plan];
     const seats = instanceStatus.seats ?? 5;
+
     const freeAssigned = Math.min(eligibleUsers.length, seats);
     const paidAssigned = eligibleUsers.length - freeAssigned;
     const paidAssignedPrice = price.user * paidAssigned;
-    const finalPrice = planPrice + paidAssignedPrice;
-    const inactive = instanceStatus.state !== InstanceState.ACTIVE;
-    const [totalCost, setTotalCost] = useState(0);
-
-    const flagEnabled = useUiFlag('displayTrafficDataUsage');
-    const [overageCost, setOverageCost] = useState(0);
 
+    const displayTrafficDataUsageEnabled = useUiFlag('displayTrafficDataUsage');
     const includedTraffic = isPro() ? proPlanIncludedRequests : 0;
     const traffic = useInstanceTrafficMetrics(currentPeriod.key);
 
-    useEffect(() => {
-        if (flagEnabled && includedTraffic > 0) {
+    const overageCost = useMemo(() => {
+        if (!displayTrafficDataUsageEnabled || !includedTraffic) {
+            return 0;
+        }
         const trafficData = toChartData(
             getDayLabels(currentPeriod.dayCount),
             traffic,
             endpointsInfo,
         );
         const totalTraffic = toTrafficUsageSum(trafficData);
-            const overageCostCalc = calculateOverageCost(
-                totalTraffic,
+        return calculateOverageCost(totalTraffic, includedTraffic);
+    }, [
+        displayTrafficDataUsageEnabled,
         includedTraffic,
-            );
-            setOverageCost(overageCostCalc);
-            setTotalCost(finalPrice + overageCostCalc);
-        } else {
-            setTotalCost(finalPrice);
-        }
-    }, [traffic]);
+        traffic,
+        currentPeriod,
+        endpointsInfo,
+    ]);
+
+    const totalCost = planPrice + paidAssignedPrice + overageCost;
+
+    const inactive = instanceStatus.state !== InstanceState.ACTIVE;
+
+    if (loading) return null;
 
     return (
         <Grid item xs={12} md={7}>
@@ -256,7 +258,7 @@ export const BillingPlan: FC<IBillingPlanProps> = ({ instanceStatus }) => {
                                     </GridCol>
                                 </GridRow>
                                 <ConditionallyRender
-                                    condition={flagEnabled && overageCost > 0}
+                                    condition={overageCost > 0}
                                     show={
                                         <GridRow>
                                             <GridCol vertical>