refactor(oidc): inline OIDC utility function

Moves the processCallback function from src/utils/oidc.ts directly into the OidcLoginButton.tsx
component where it is used. The now-empty oidc.ts utility file has been removed. This improves code
co-location as the function is only used in a single place.

Addresses https://github.com/fallenbagel/jellyseerr/pull/1505#discussion_r2194982515

src/components/Login/OidcLoginButton.tsx

@@ -1,7 +1,6 @@
 import defineMessages from '@app/utils/defineMessages';
-import { processCallback } from '@app/utils/oidc';
 import type { PublicOidcProvider } from '@server/lib/settings';
-import axios from 'axios';
+import axios, { isAxiosError } from 'axios'; // <-- isAxiosError is now needed here
 import { useRouter, useSearchParams } from 'next/navigation';
 import { useCallback, useEffect, useState } from 'react';
 import { useIntl } from 'react-intl';
@@ -11,6 +10,33 @@ const messages = defineMessages('components.Login', {
   oidcLoginError: 'An error occurred while logging in with {provider}.',
 });
 
+// The function from src/utils/oidc.ts is now here as a local helper
+async function processCallback(params: URLSearchParams, provider: string) {
+  const url = new URL(
+    `/api/v1/auth/oidc/callback/${encodeURIComponent(provider)}`,
+    window.location.origin
+  );
+  url.search = params.toString();
+
+  try {
+    const res = await axios.get(url.toString());
+
+    return {
+      type: 'success',
+      message: res.data,
+    };
+  } catch (e) {
+    if (isAxiosError(e) && e.response?.data?.message) {
+      return { type: 'error', message: e.response.data.message };
+    }
+
+    return {
+      type: 'error',
+      message: e.message,
+    };
+  }
+}
+
 type OidcLoginButtonProps = {
   provider: PublicOidcProvider;
   onError?: (message: string) => void;
@@ -43,6 +69,7 @@ export default function OidcLoginButton({
   }, [provider, intl, onError]);
 
   const handleCallback = useCallback(async () => {
+    // This now calls the local helper function
     const result = await processCallback(searchParams, provider.slug);
     if (result.type === 'success') {
       // redirect to homepage

src/utils/oidc.ts

@@ -1,35 +0,0 @@
-import axios, { isAxiosError } from 'axios'; // <-- Import axios and isAxiosError
-
-export async function processCallback(
-  params: URLSearchParams,
-  provider: string
-) {
-  const url = new URL(
-    `/api/v1/auth/oidc/callback/${encodeURIComponent(provider)}`,
-    window.location.origin
-  );
-  url.search = params.toString();
-
-  try {
-    // The fetch call is replaced with axios.get.
-    // On success, the JSON response is automatically parsed and available in res.data.
-    const res = await axios.get(url.toString());
-
-    return {
-      type: 'success',
-      message: res.data,
-    };
-  } catch (e) {
-    // Axios throws an error for non-2xx responses. We can check if it's an axios error
-    // to safely access the error message from the server's response payload.
-    if (isAxiosError(e) && e.response?.data?.message) {
-      return { type: 'error', message: e.response.data.message };
-    }
-
-    // Fallback for generic errors
-    return {
-      type: 'error',
-      message: e.message,
-    };
-  }
-}