OAuth 2 Access token generation from Azure Function

[bentura]

Hi everyone,

I'm having a nightmare trying to use the OAuth 2 Access token generation in APIGee from an Azure Function.

So I have an Azure Function coded in C# using Rest sharp which is calling out API Proxy to get an Access token.  We use this proxy in other applications and it works fine.  We are using client_crendtial grant type.  When I run the application locally I am able to get an access toekn with no issue in Postman or the browser, but when I publish it to the azure function, I get the following error:

{"Error":"Client credentials are required","ErrorCode":"invalid_client"}

 I have found other Questions on this forum regarding this, and I think I have tried every combination of Parameters, headers etc in my request with no luck.

I've done:

• set the header content-type to application/x-www-form-urlencoded
• sent the client_id and secret in base64 and plain text with a : in the middle
• sent the client_id on its own in the body
• turned off all authorisation on the azure function incase that was the issue but I get the same error in the output whilst it works locally still.
• sent Basic auth credtials alongside all of the options above
• Created a new policy in APIGee with pass through 
• Removed the authorization header from the flow before the oauth policy
• forced apigee to look in the policy for client_id in formparam  using this:

  <ClientId>request.formparam.client_id</ClientId>

  I think thats everything I have tried.

Are there any specific issues that anyone is aware of when using an Azure Function to call APIGee like this?  It's such a simple function which works fine locally so I know that the code can talk to APIgee and get the repsonse I want.

Thanks