fix(jans-pycloudlib): re-running set_all method overwrites existing secrets/configs in AWS Secrets

[iromli]

Describe the bug

Re-running configurator load command overwrites existing secrets/configs. Due to the behavior of string-based payload, there's no such concept of merge-with-existing data.

To Reproduce

Steps to reproduce the behavior:

1. Deploy janssenproject/configurator with load command (choose aws adapter)
2. Wait until configs and secrets pushed to AWS Secret Manager
3. Deploy janssenproject/persistence; this will push other secrets/configs not created in step 1
4. Repeat step 1 and 2
5. Check secrets and configs (data created in step 3 are missing)

Expected behavior

Re-running janssenproject/configurator load command merges new data with existing ones.