Bug: rename the browser name header to `x-browser-name`



Rename the browser name header from `browsername` to `x-browser-name`
diff --git a/crates/router/src/lib.rs b/crates/router/src/lib.rs
index f0d332514d1..7059f0451ba 100644
--- a/crates/router/src/lib.rs
+++ b/crates/router/src/lib.rs
@@ -77,7 +77,7 @@ pub mod headers {
     pub const X_CLIENT_SOURCE: &str = "X-Client-Source";
     pub const X_PAYMENT_CONFIRM_SOURCE: &str = "X-Payment-Confirm-Source";
     pub const CONTENT_LENGTH: &str = "Content-Length";
-    pub const BROWSER_NAME: &str = "browsername";
+    pub const BROWSER_NAME: &str = "x-browser-name";
     pub const X_CLIENT_PLATFORM: &str = "x-client-platform";
 }
 

## 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 -->
Rename the browser name header from `browsername` to `x-browser-name`
Our web sdk is currently passing  `browsername` also, but this will be removed going forward
<img width="716" alt="image" src="https://github.com/juspay/hyperswitch/assets/83439957/e58c0601-0cba-4dfb-ab28-e21337227f2d">


### Additional Changes

- [ ] 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).
-->


## 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)?
-->
-> Create merchant connector account with apple pay manual flow. Below is the metadata for the manual flow.
```
"session_token_data": {
                    "initiative": "web",
                    "certificate": "==",
                    "display_name": "applepay",
                    "certificate_keys": "",
                    "payment_processing_details_at": "Hyperswitch",
                    "payment_processing_certificate": "",
                    "payment_processing_certificate_key": "",
                    "initiative_context": "sdk-test-app.netlify.app",
                    "merchant_identifier": "",
                    "merchant_business_country": "US"
                }
```

-> Session response when only `x-client-platform` is passed
```
curl --location 'http://localhost:8080/payments/session_tokens' \
--header 'Content-Type: application/json' \
--header 'x-client-platform: web' \
--header 'api-key: pk_dev_7e0d9f48e20b430baa86eb956dc99142' \
--data '{
    "payment_id": "pay_7WAejcRN248R0Y7Kwsfh",
    "wallets": [],
    "client_secret": "pay_7WAejcRN248R0Y7Kwsfh_secret_CDL03LbGwQQnMPVA0Lq0"
}'
```
<img width="903" alt="image" src="https://github.com/juspay/hyperswitch/assets/83439957/b3a377eb-078b-4c3f-849d-2ebc8083a91c">

-> Session response when `x-client-platform` and `x-browser-name` are passed as `web` and `Safari`
```
curl --location 'http://localhost:8080/payments/session_tokens' \
--header 'Content-Type: application/json' \
--header 'x-browser-name: Safari' \
--header 'x-client-platform: web' \
--header 'api-key: pk_dev_9754f74226e84eecbe72e09dc3890360' \
--data '{
    "payment_id": "pay_aPyo8BbO9sjayVJ75O0B",
    "wallets": [],
    "client_secret": "pay_aPyo8BbO9sjayVJ75O0B_secret_IHwD3t4hMolns4eIKIep"
}'
```
<img width="1112" alt="image" src="https://github.com/juspay/hyperswitch/assets/83439957/6b298647-95c1-496e-b75b-135dcc9e86f0">

-> When only is `x-client-platform: ios`
```
curl --location 'http://localhost:8080/payments/session_tokens' \
--header 'Content-Type: application/json' \
--header 'x-client-platform: ios' \
--header 'api-key: pk_dev_30a379e8af2d46f6be977b01d8b38708' \
--data '{
    "payment_id": "pay_CGA1yXcMIArRqgn9ZyuD",
    "wallets": [],
    "client_secret": "pay_CGA1yXcMIArRqgn9ZyuD_secret_A2MRtOhcSzFGhEeEukRv"
}'
```
<img width="956" alt="image" src="https://github.com/juspay/hyperswitch/assets/83439957/f36d61b5-8c59-4526-818f-f834262cbccf">


## 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`
- [x] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
