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QuestionIs there any way to automate the authorization code grant token that does not rely on the user having to give permission via a login eBay web-page?
No, there is no way to generate the authorization code grant token without getting user consent. You need to get the consent from the user at least once as you cannot generate a user access token without getting the user consent.
For more comprehensive information, please refer to this API documentation: https://developer.ebay.com/api-docs/static/oauth-auth-code-grant-request.html
Authorization code grant process returns a refresh_token which is a long-lived value that you can use to update an expired User access token. This means you do not have to get the user's consent each time you need a new User access token. You can store this refresh_token and you can update an expired User access token.
For in-depth insights, refer to the Refresh Token API documentation: https://developer.ebay.com/api-docs/static/oauth-refresh-token-request.html
OAuth best practices: https://developer.ebay.com/api-docs/static/oauth-best-practices.html