Are there any good examples of a custom mapper? I see in the docs that https://github.com/transferwise/pipelinewise-transform-field is one example. Does the meltano SDK have any support for bootstrapping a custom mapping plugin? I have data in a source mongodb database that was encrypted by an application. I’m interested to create a custom mapper that can decrypt that data between a tap and target command, so that it can be encrypted in the target database using that database’s native encryption support. My encryption key is in AWS SecretsManager so I’m thinking about a mapper that will fetch the necessary secret upon startup and then use that to do the decription of each record passing through the mapper, as appropriate.

I haven't built a custom transformer but we use meltano-map-transformer... I imagine you could use that as a starting point.

thanks - it looks like the SDK does provide a base class too https://github.com/meltano/sdk/blob/main/singer_sdk/mapper_base.py