Allow use of other secrets providers

[moensch]

Is this a request for help?: No

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Is this a BUG REPORT or FEATURE REQUEST? (choose one): Feature Request

Currently, the chart insists that the .agent.token is provided, and it creates a Secret. We would like to use a CRD to provide our own secret, such as external-secrets.io.

The Chart should be updated to optionally reference an existing secret, and not depend on the in-house secret.