fix: [IOPID-2543] Add logic to merge data during zendesk polling (#6515)

## Short description
In the as-is when polling, the data in the redux store was overwritten
and the zendeskToken was no longer available. This led to an error when
sending messages to support, within the chat with support. (only for
logged in users)

## Demo
| .env.local | .env.production |
| - | - |
| <video
src="https://github.com/user-attachments/assets/4580715e-08f7-488d-9146-27b424efaa97"/>
| <video
src="https://github.com/user-attachments/assets/6d1b63d3-5c3f-4aa1-baeb-4029dfa2e6e4"/>
|

> [!Warning]
> In order to test this PR using .env.local, you need to use this branch
on the dev-server pagopa/io-dev-api-server#445

## How to test
Run the application using or .env.local or .env.production or both
Activate the fast-login settings 
follow the video demo

ts/features/zendesk/saga/index.ts

@@ -51,7 +51,8 @@ function* zendeskGetSessionPollingLoop(
     const checkSessionResponse = yield* call(
       checkSession,
       getSession,
-      formatRequestedTokenString()
+      formatRequestedTokenString(),
+      true
     );
     if (checkSessionResponse === 401) {
       break;

ts/sagas/startup/__tests__/watchCheckSessionSaga.test.ts

@@ -13,6 +13,7 @@ import {
 } from "../watchCheckSessionSaga";
 import { handleSessionExpiredSaga } from "../../../features/fastLogin/saga/utils";
 import { isFastLoginEnabledSelector } from "../../../features/fastLogin/store/selectors";
+import { sessionInfoSelector } from "../../../store/reducers/authentication";
 
 describe("checkSession", () => {
   const getSessionValidity = jest.fn();
@@ -29,7 +30,7 @@ describe("checkSession", () => {
 
     const fields = "(zendeskToken,walletToken,lollipopAssertionRef)";
 
-    testSaga(testableCheckSession!, getSessionValidity, fields)
+    testSaga(testableCheckSession!, getSessionValidity, fields, false)
       .next()
       .call(getSessionValidity, { fields })
       .next(responseOK)
@@ -39,6 +40,8 @@ describe("checkSession", () => {
         })
       )
       .next()
+      .select(sessionInfoSelector)
+      .next()
       .put(sessionInformationLoadSuccess(responseValue as PublicSession))
       .next()
       .isDone();
@@ -49,7 +52,7 @@ describe("checkSession", () => {
 
     const fields = "(zendeskToken,walletToken,lollipopAssertionRef)";
 
-    testSaga(testableCheckSession!, getSessionValidity, fields)
+    testSaga(testableCheckSession!, getSessionValidity, fields, false)
       .next()
       .call(getSessionValidity, { fields })
       .next(responseUnauthorized)
@@ -67,7 +70,7 @@ describe("checkSession", () => {
 
     const fields = undefined;
 
-    testSaga(testableCheckSession!, getSessionValidity, fields)
+    testSaga(testableCheckSession!, getSessionValidity, fields, false)
       .next()
       .call(getSessionValidity, { fields })
       .next(response500)
@@ -89,7 +92,7 @@ describe("checkSession", () => {
 
     const fields = "(zendeskToken,walletToken,lollipopAssertionRef)";
 
-    testSaga(testableCheckSession!, getSessionValidity, fields)
+    testSaga(testableCheckSession!, getSessionValidity, fields, false)
       .next()
       .call(getSessionValidity, { fields })
       .next(responseLeft)

ts/sagas/startup/watchCheckSessionSaga.ts

@@ -1,8 +1,9 @@
 import { readableReport } from "@pagopa/ts-commons/lib/reporters";
 import { TypeOfApiResponseStatus } from "@pagopa/ts-commons/lib/requests";
 import * as E from "fp-ts/lib/Either";
+import * as O from "fp-ts/lib/Option";
 import { SagaIterator } from "redux-saga";
-import { call, put, takeLatest } from "typed-redux-saga/macro";
+import { call, put, select, takeLatest } from "typed-redux-saga/macro";
 import { getType } from "typesafe-actions";
 import { GetSessionStateT } from "../../../definitions/session_manager/requestTypes";
 import { BackendClient } from "../../api/backend";
@@ -14,10 +15,13 @@ import { ReduxSagaEffect, SagaCallReturnType } from "../../types/utils";
 import { isTestEnv } from "../../utils/environment";
 import { convertUnknownToError } from "../../utils/errors";
 import { handleSessionExpiredSaga } from "../../features/fastLogin/saga/utils";
+import { getOnlyNotAlreadyExistentValues } from "../../features/zendesk/utils";
+import { sessionInfoSelector } from "../../store/reducers/authentication";
 
 export function* checkSession(
   getSessionValidity: ReturnType<typeof BackendClient>["getSession"],
-  fields?: string // the `fields` parameter is optional and it defaults to an empty object
+  fields?: string, // the `fields` parameter is optional and it defaults to an empty object
+  mergeOldAndNewValues: boolean = false
 ): Generator<
   ReduxSagaEffect,
   TypeOfApiResponseStatus<GetSessionStateT> | undefined,
@@ -40,7 +44,18 @@ export function* checkSession(
       );
 
       if (response.right.status === 200) {
-        yield* put(sessionInformationLoadSuccess(response.right.value));
+        const currentSessionInfo = yield* select(sessionInfoSelector);
+
+        yield* put(
+          sessionInformationLoadSuccess(
+            mergeOldAndNewValues && O.isSome(currentSessionInfo)
+              ? getOnlyNotAlreadyExistentValues(
+                  response.right.value,
+                  currentSessionInfo.value
+                )
+              : response.right.value
+          )
+        );
       }
       return response.right.status;
     }