Invalid webhook request payload

### Environment

SaaS (https://sentry.io/)

### Steps to Reproduce

Since the 27th of February, webhook payloads sent to the endpoint set in an internal integration are not correctly formated. The issue seems to be due to characters not being escaped.

So far the I was unable to reproduce.

Due to possible PII involved, I'm adding the information to the shadow Jira ticket.

### Expected Result

All characters are correctly escaped and the payload is correctly formatted for 3rd party to process.

### Actual Result

Incorrect format causes issues during webhook payload processing.

### Product Area

Settings - Developer Settings

### Link

_No response_

### DSN

_No response_

### Version

_No response_

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-2141) by [Unito](https://www.unito.io)