update readme

Author: nosovk

readme.md

@@ -4,6 +4,22 @@ Goal: implement sending data from 1c to Google BigQuery
 Problem: 1C can't generate session key for connection to BigQuery
 Resolution: create REST function for handling session key creation
 
+# Api
+Endpoint deployed at `https://bigquery-1c.web.app/sign`
+
+### Request format
+```json
+{"pem": "key",
+"body": "body to encrypt"}
+```
+### Responce format
+```json
+{"code": "status code",
+"message": "result, is digest or error"
+}
+```
+On successful execution `code` is `200` and message will contain digest.
+On error mostly 500 or 400 code will be thrown.
 
 ## To create one line PEM
 Api accepts json, to pass multiline string in json you need to convert newlines to `\n`.
@@ -20,5 +36,7 @@ curl --location --request POST 'https://bigquery-1c.web.app/sign' \
 --data-raw '{"pem": "-----BEGIN RSA PRIVATE KEY-----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\nhOqU+7yhUj88M2D2gd/JTlp1XI6GfhH+Y7sUdGKP/g==\n-----END RSA PRIVATE KEY-----\n","body": "body"}'
 ```
 
+
+
 ## todo
 - 1c example