We have web application that need to read & write data to Salesforce. For that, Web application have to authenticate with Salesforce and get access token.
I refer all authentication flow mentioned at Salesforce community. As per the Web application requirement, in our case, there would be no user interaction that login to salesforce application and allow to access. We have already implemented the Username-Password flow but it would require "Security Token" and in some cases due to security concerns some of the customers wouldn't able to generate(in case of SSO) or deny to share it. Additionally, Salesforce doesn't support Username-Password flow method.
So please suggest the alternative suitable authentication flow that authorize the request and receive access_token.