Rotate database password stored in a file using AWS Secrets Manager

Question

I'm currently deploying Owncloud onto an EC2 instance in AWS. Owncloud used RDS for the database and it stored the connection credentials (user, password) in plain text in a configuration file. Owncloud will use that credential in the configuration file to authenticate to RDS.

Now I was asked to rotate the database password every once in a while using the Secret Manager. Ideally we have to update the source code of our application to retrieve the database password from Secret Manager. The problem is I am not able to modify Owncloud's code to get the password from Secret Manager, it only reads the password from the configuration file.

So how would I do the password rotation in this case? Do I edit the Lambda rotation function to update the Owncloud configuration file on the EC2 using SSM? That seems like a hard way and I don't have a better idea for now. Any help would be appreciated :)

Thank you and have a great day.

I tried to find a way to make Owncloud to get the password from AWS Secret Manager instead of the plain text password from the configuration file. I wasn't succeed to do so.