Issue:
Bug: Change Underscore(_) to hyphen(-) in payment link locale.



Change Underscore(_) to hyphen(-) in payment link locale.

Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Change Underscore(_) to hyphen(-) in payment link locale according to ISO standards.

### Additional Changes

- [x] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide links to the files with corresponding changes.

Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
-->


## Motivation and Context
<!--
Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless it is an obvious bug or documentation fix
that will have little conversation).
-->
We need to follow ISO standards when accepting the locale for payment links.


## How did you test it?
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
-->
```
curl --location 'http://localhost:8080/payments' \
--header 'Content-Type: application/json' \
--header 'Accept: application/json' \
--header 'api-key: **' \
--header 'Accept-Language: zh-hant' \
--data '{
    "amount": 10,
    "setup_future_usage": "off_session",
    "currency": "EUR",
    "payment_link": true,
    "session_expiry": 60,
    "return_url": "https://google.com",
    "payment_link_config": {
        "theme": "#14356f",
        "logo": "https://logo.com/wp-content/uploads/2020/08/zurich.svg",
        "seller_name": "Zurich Inc."
    }
}'
```
```
zh-hant - should see traditional chinese
zh_hant - english
zh-hant-abcdef - traditional chinese
zh - simplified chinese
Zh - simplified chinese
ZH-HANT - traditional chinese
zh-abcdef - simplified chinese
```
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/a1c25820-6e50-480f-96f6-5a831a856bfd" />
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/1db9322d-601e-49df-bf2f-6e5f1911d4cd" />
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/d934116c-a24a-479d-86e6-9f0b25028400" />


## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [ ] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible


Testing:

```
curl --location 'http://localhost:8080/payments' \
--header 'Content-Type: application/json' \
--header 'Accept: application/json' \
--header 'api-key: **' \
--header 'Accept-Language: zh-hant' \
--data '{
    "amount": 10,
    "setup_future_usage": "off_session",
    "currency": "EUR",
    "payment_link": true,
    "session_expiry": 60,
    "return_url": "https://google.com",
    "payment_link_config": {
        "theme": "#14356f",
        "logo": "https://logo.com/wp-content/uploads/2020/08/zurich.svg",
        "seller_name": "Zurich Inc."
    }
}'
```
```
zh-hant - should see traditional chinese
zh_hant - english
zh-hant-abcdef - traditional chinese
zh - simplified chinese
Zh - simplified chinese
ZH-HANT - traditional chinese
zh-abcdef - simplified chinese
```
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/a1c25820-6e50-480f-96f6-5a831a856bfd" />
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/1db9322d-601e-49df-bf2f-6e5f1911d4cd" />
<img width="2560" height="1440" alt="image" src="https://github.com/user-attachments/assets/d934116c-a24a-479d-86e6-9f0b25028400" />

Patch:
diff --git a/crates/router/src/core/payment_link/locale.js b/crates/router/src/core/payment_link/locale.js
index 1b2d5c4108b..46103ea9fc5 100644
--- a/crates/router/src/core/payment_link/locale.js
+++ b/crates/router/src/core/payment_link/locale.js
@@ -3,11 +3,11 @@ The languages supported by locale.js are:
  1) English (en)
  2) Hebrew (he)
  3) French (fr)
- 4) British English (en_gb)
+ 4) British English (en-gb)
  5) Arabic (ar)
  6) Japanese (ja)
  7) German (de)
- 8) Belgian French (fr_be)
+ 8) Belgian French (fr-be)
  9) Spanish (es)
  10) Catalan (ca)
  11) Portuguese (pt)
@@ -17,7 +17,7 @@ The languages supported by locale.js are:
  15) Swedish (sv)
  16) Russian (ru)
  17) Chinese (zh)
- 19) Traditional Chinese (zh_hant)
+ 19) Traditional Chinese (zh-hant)
 */
 const locales = {
     en: {
@@ -119,7 +119,7 @@ const locales = {
       errorCode: "Code d'erreur",
       errorMessage: "Message d'erreur"
     },
-    en_gb: {
+    "en-gb": {
       expiresOn: "Link expires on: ",
       refId: "Ref Id: ",
       requestedBy: "Requested by ",
@@ -151,7 +151,6 @@ const locales = {
       notAllowed: "You are not allowed to view this content.",
       errorCode: "Error code",
       errorMessage: "Error Message"
-      
     },
     ar: {
       expiresOn: "الرابط ينتهي في: ",
@@ -252,7 +251,7 @@ const locales = {
       errorCode: "Fehlercode",
       errorMessage: "Fehlermeldung"
     },
-    fr_be: {
+    "fr-be": {
       expiresOn: "Le lien expire le: ",
       refId: "ID de référence: ",
       requestedBy: "Demandé par ",
@@ -284,7 +283,6 @@ const locales = {
       notAllowed: "Vous n'êtes pas autorisé à voir ce contenu.",
       errorCode: "Code d'erreur",
       errorMessage: "Message d'erreur"
-      
     },
     es: {
       expiresOn: "El enlace expira el: ",
@@ -384,7 +382,6 @@ const locales = {
       notAllowed: "Você não tem permissão para ver este conteúdo.",
       errorCode: "Código de erro",
       errorMessage: "Mensagem de erro"
-
     },
     it: {
       expiresOn: "Link scade il: ",
@@ -584,7 +581,7 @@ const locales = {
       errorCode: "错误代码",
       errorMessage: "错误信息"
     },
-    zh_hant: {
+    "zh-hant": {
       expiresOn: "連結到期日期：",
       refId: "參考編號：",
       requestedBy: "請求者 ",
@@ -628,10 +625,11 @@ function getLanguage(localeStr) {
   var language = parts[0];
   var country = parts.length > 1 ? parts[1] : null;
 
-  var key = `${language}_${country}`;
+  var key = language + '-' + country;
   switch (key) {
-    case 'en_gb': return 'en_gb';
-    case 'fr_be': return 'fr_be';
+    case 'en-gb': return 'en-gb';
+    case 'fr-be': return 'fr-be';
+    case 'zh-hant': return 'zh-hant';
     default: return language;
   }
 }