Automating OAuth 1.0 Authorization header for Sellsy CRM API integration

Hello callin.io Community!

I'm a beginner in automation from France and I'm looking for some assistance with a challenging OAuth 1.0 integration (at least for me ).

My Goal

My objective is to automate API calls to my CRM, Sellsy, using callin.io’s HTTP module. The integration functions flawlessly when I manually construct the OAuth 1.0 Authorization header in Postman, but I'm struggling to automate this header generation within callin.io.

What Works (Manual Process)

In Postman, I can successfully generate the following OAuth 1.0 Authorization header:
"
OAuth oauthconsumerkey=“…”,oauthtoken=“…”,oauthsignaturemethod=“HMAC-SHA1”,oauthtimestamp=“1749217218”,oauthnonce=“SJ3HbEVKegK”,oauthversion=“1.0”,oauth_signature=“e%2FLrQh74zijApFt4SV1Qtp1S%2FBQ%3D”
"

My Current Scenario Setup

1. Compose a string: Used for generating the OAuth nonce.
2. JavaScript module: Where I'm attempting to generate the HMAC-SHA1 signature.
3. HTTP module: Used for making the API call to Sellsy.

The Problem

I've experimented with AI assistants (GPT-4-mini and Claude 4) to produce JavaScript code for the HMAC-SHA1 signature, but I consistently encounter errors such as: SyntaxError: ‘return’ outside of function, ReferenceError: CryptoJS is not defined, Empty Output / No Result in Bundle, SyntaxError: Missing semicolon, and Still Empty Output After Fixing Syntax, among others.

What I’ve Tried

• Several JavaScript implementations for OAuth signature generation.
• Different methods for structuring the code within callin.io’s JavaScript environment.
• Various approaches suggested by AI tools.

What I Need Help With

1. Guidance on how to correctly generate the oauth_signature using HMAC-SHA1 within callin.io’s JavaScript environment, or alternative solutions.
2. The proper way to structure the JavaScript code to ensure it functions correctly within callin.io.
3. Any available working examples of OAuth 1.0 automation for Sellsy or comparable CRMs.

Additional Info

• I possess the consumer key, consumer secret, token, and token secret from Sellsy.
• API calls function perfectly in Postman when using manual OAuth headers.
• I am willing to share screenshots of my scenario if it would be beneficial.

Has anyone successfully automated OAuth 1.0 signatures in callin.io before? Any advice would be greatly appreciated!

Merci beaucoup!