Add link to HyTEST docs (#205)

These docs inspired a lot of the docs here and I just want to link users who want to read more there.

book/guides/data_guide.md

@@ -95,6 +95,10 @@ Ideally we want to store these secrets only in one central location. The natural
 According to those issues we can only make the aws profiles (or [source profiles?](https://forum.rclone.org/t/s3-profile-failing-when-explicit-s3-endpoint-is-present/36063/4?u=jbusecke), anyways the credentials part of it) work if we define one config file per remote [and use the 'default' profile](https://forum.rclone.org/t/shared-credentials-file-is-not-recognised/46993/2?u=jbusecke)which presumably breaks compatibility with fsspec, and also does not work at all right now. So at the moment we will have to keep the credentials in two separate spots 🤷‍♂️. **Please make sure to apply proper caution when [handling secrets](guide.code.secrets) for each config files that stores secrets in plain text!**
 :::
 
+:::\{note}
+You can find more great documentation, specifically on how to use OSN resources, in [this section](https://hytest-org.github.io/hytest/essential_reading/DataSources/Data_S3.html#credentialed-access) of the [HyTEST Docs](https://hytest-org.github.io/hytest/doc/About.html#)
+:::
+
 (hub.data.setup)=
 
 ###