Call API method PUT from POST or vise versa

I know what both PUT and POST method is and use for, but I wanted to know a few things in my current scenarios.

Just before that, brief out about my API:

• POST endpoint for insert new records and in request body has existing record client will get the duplicate and ask for do the PUT as record already exists.

• PUT for updating my existing records and if not existing record is coming on the body client will get the message to use POST as the record is new one.

• GET for comment select operations

Our use case -

we wanted to automate this API interaction, I used PostMan for all my development/testing part.

Now, I am writing the Azure DevOps pipeline to automate the insert and update stuff for this I would get the input from one repository which the user will update with required input, the input will be in the JSON format. I will have one bash script for checkout the inputs repository and I will loop through the all input JSONs and will those API.

My question is - as I have a separate endpoint for insert and update... so how I can automate it as from the pipeline? I would gonna call one POST/PUT for the given JSON input.

Should I have to write PUT call within the POST method when I find data having already existed and same in case of PUT if an incoming record is new I should have to call POST method instead.

I think this will violate the separation of concern principle for any of the method.

let me know what is the best way to deal this condition with best practices.