Signature is hash value of the request body salted with your SECRET_TOKEN assigned by Leanpay.

To create hash follow these steps:
1. Create string in format: ENDPOINT_URL + SECRET_TOKEN + RAW_BODY_PAYLOAD
2. Hash this string using SHA256 algorithm

Example

SECRET_TOKEN provided by Leanpay: mysecrettoken

RAW_BODY_PAYLOAD:
{
  "param1": "value1",
  "param2": "value2",
  "param3": "value3"
}

ENDPOINT_URL: https://leanpay.com/example

Now, string for SHA256 will look like this:
https://leanpay.com/examplemysecrettoken{
  "param1": "value1",
  "param2": "value2",
  "param3": "value3"
}

Result hex: 1710009175f64afa322281b48d460e117aff65d52db12253bdfc75a9d866fecd